diff --git a/src/OutlookAddin.Core/Models/EspoListResponse.cs b/src/OutlookAddin.Core/Models/EspoListResponse.cs
new file mode 100644
index 0000000..c4cf6e1
--- /dev/null
+++ b/src/OutlookAddin.Core/Models/EspoListResponse.cs
@@ -0,0 +1,14 @@
+using System.Collections.Generic;
+using System.Text.Json.Serialization;
+
+namespace MarcusLaw.OutlookAddin.Core.Models
+{
+    public sealed class EspoListResponse<T>
+    {
+        [JsonPropertyName("total")]
+        public int Total { get; set; }
+
+        [JsonPropertyName("list")]
+        public List<T> List { get; set; } = new List<T>();
+    }
+}
diff --git a/src/OutlookAddin.Core/Models/MatchResult.cs b/src/OutlookAddin.Core/Models/MatchResult.cs
new file mode 100644
index 0000000..c5c04ff
--- /dev/null
+++ b/src/OutlookAddin.Core/Models/MatchResult.cs
@@ -0,0 +1,22 @@
+using System;
+using System.Collections.Generic;
+
+namespace MarcusLaw.OutlookAddin.Core.Models
+{
+    public sealed class MatchResult
+    {
+        public string SenderEmail { get; set; } = string.Empty;
+
+        public ContactEntity? Contact { get; set; }
+
+        public AccountEntity? Account { get; set; }
+
+        public List<CaseEntity> RecentCases { get; set; } = new List<CaseEntity>();
+
+        public bool IsAmbiguous { get; set; }
+
+        public int CandidateCount { get; set; }
+
+        public DateTimeOffset RetrievedAt { get; set; } = DateTimeOffset.UtcNow;
+    }
+}
diff --git a/src/OutlookAddin.Core/Services/EspoCrmClient.cs b/src/OutlookAddin.Core/Services/EspoCrmClient.cs
index 8b28f8f..57b7b6e 100644
--- a/src/OutlookAddin.Core/Services/EspoCrmClient.cs
+++ b/src/OutlookAddin.Core/Services/EspoCrmClient.cs
@@ -155,6 +155,20 @@ namespace MarcusLaw.OutlookAddin.Core.Services
         public Task<UserInfo> TestConnectionAsync(CancellationToken cancellationToken = default)
             => GetJsonAsync<UserInfo>("App/user", cancellationToken);
 
+        public Task<EspoListResponse<CaseEntity>> ListCasesForContactAsync(string contactId, int maxSize = 5, CancellationToken cancellationToken = default)
+        {
+            if (string.IsNullOrWhiteSpace(contactId)) throw new ArgumentException("contactId required", nameof(contactId));
+            if (maxSize <= 0) maxSize = 5;
+            var path =
+                "Case?select=" + Uri.EscapeDataString("id,name,number,status,createdAt,accountId") +
+                "&where[0][type]=linkedWith" +
+                "&where[0][attribute]=contacts" +
+                "&where[0][value]=" + Uri.EscapeDataString(contactId) +
+                "&orderBy=createdAt&order=desc" +
+                "&maxSize=" + maxSize;
+            return GetJsonAsync<EspoListResponse<CaseEntity>>(path, cancellationToken);
+        }
+
         public async Task<ContactEntity> CreateContactAsync(string name, string? emailAddress = null, CancellationToken cancellationToken = default)
         {
             if (string.IsNullOrWhiteSpace(name)) throw new ArgumentException("name required", nameof(name));
diff --git a/src/OutlookAddin.Core/Services/IEspoCrmClient.cs b/src/OutlookAddin.Core/Services/IEspoCrmClient.cs
index 37d3207..7726955 100644
--- a/src/OutlookAddin.Core/Services/IEspoCrmClient.cs
+++ b/src/OutlookAddin.Core/Services/IEspoCrmClient.cs
@@ -13,6 +13,7 @@ namespace MarcusLaw.OutlookAddin.Core.Services
         Task<AccountEntity> GetAccountAsync(string id, string? select = null, CancellationToken cancellationToken = default);
         Task<ContactEntity> GetContactAsync(string id, string? select = null, CancellationToken cancellationToken = default);
         Task<ContactEntity> CreateContactAsync(string name, string? emailAddress = null, CancellationToken cancellationToken = default);
+        Task<EspoListResponse<CaseEntity>> ListCasesForContactAsync(string contactId, int maxSize = 5, CancellationToken cancellationToken = default);
         Task<UserInfo> TestConnectionAsync(CancellationToken cancellationToken = default);
     }
 }
diff --git a/src/OutlookAddin.Core/Services/IMatchingService.cs b/src/OutlookAddin.Core/Services/IMatchingService.cs
new file mode 100644
index 0000000..60d7182
--- /dev/null
+++ b/src/OutlookAddin.Core/Services/IMatchingService.cs
@@ -0,0 +1,18 @@
+using System.Threading;
+using System.Threading.Tasks;
+using MarcusLaw.OutlookAddin.Core.Models;
+
+namespace MarcusLaw.OutlookAddin.Core.Services
+{
+    public interface IMatchingService
+    {
+        /// <summary>
+        /// Looks up the contact/account/recent-cases bundle for a sender
+        /// email address. Returns null when there is no unique Contact match
+        /// (0 or 2+ candidates). Results are cached for 10 minutes.
+        /// </summary>
+        Task<MatchResult?> LookupAsync(string senderEmail, CancellationToken cancellationToken = default);
+
+        void Invalidate(string senderEmail);
+    }
+}
diff --git a/src/OutlookAddin.Core/Services/MatchingService.cs b/src/OutlookAddin.Core/Services/MatchingService.cs
new file mode 100644
index 0000000..e0cfe1a
--- /dev/null
+++ b/src/OutlookAddin.Core/Services/MatchingService.cs
@@ -0,0 +1,122 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using MarcusLaw.OutlookAddin.Core.Models;
+using Microsoft.Extensions.Caching.Memory;
+using Serilog;
+
+namespace MarcusLaw.OutlookAddin.Core.Services
+{
+    public sealed class MatchingService : IMatchingService
+    {
+        private static readonly TimeSpan CacheExpiry = TimeSpan.FromMinutes(10);
+        private const string ContactSelect = "id,name,emailAddress,accountId,accountName";
+
+        private readonly IEspoCrmClient _client;
+        private readonly IMemoryCache _cache;
+        private readonly ILogger _logger;
+
+        public MatchingService(IEspoCrmClient client, IMemoryCache cache, ILogger logger)
+        {
+            _client = client ?? throw new ArgumentNullException(nameof(client));
+            _cache = cache ?? throw new ArgumentNullException(nameof(cache));
+            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+        }
+
+        public async Task<MatchResult?> LookupAsync(string senderEmail, CancellationToken cancellationToken = default)
+        {
+            if (string.IsNullOrWhiteSpace(senderEmail)) return null;
+            if (!senderEmail.Contains("@")) return null;
+
+            var key = CacheKey(senderEmail);
+            if (_cache.TryGetValue<MatchResult?>(key, out var cached))
+            {
+                return cached;
+            }
+
+            try
+            {
+                var search = await _client.EmailAddressSearchAsync(senderEmail, "Contact", cancellationToken).ConfigureAwait(false);
+
+                if (search.List.Count == 0)
+                {
+                    _cache.Set(key, (MatchResult?)null, CacheExpiry);
+                    return null;
+                }
+
+                if (search.List.Count > 1)
+                {
+                    var ambiguous = new MatchResult
+                    {
+                        SenderEmail = senderEmail,
+                        IsAmbiguous = true,
+                        CandidateCount = search.List.Count
+                    };
+                    _cache.Set<MatchResult?>(key, ambiguous, CacheExpiry);
+                    return ambiguous;
+                }
+
+                var contactRef = search.List[0];
+                var contact = await _client.GetContactAsync(contactRef.Id, ContactSelect, cancellationToken).ConfigureAwait(false);
+
+                AccountEntity? account = null;
+                if (!string.IsNullOrWhiteSpace(contact.AccountId))
+                {
+                    try
+                    {
+                        account = await _client.GetAccountAsync(contact.AccountId!, "id,name,emailAddress", cancellationToken).ConfigureAwait(false);
+                    }
+                    catch (Exception ex)
+                    {
+                        _logger.Warning(ex, "MatchingService: failed to load account {AccountId} for {Email}", contact.AccountId, senderEmail);
+                    }
+                }
+
+                var cases = new System.Collections.Generic.List<CaseEntity>();
+                try
+                {
+                    var list = await _client.ListCasesForContactAsync(contact.Id, 5, cancellationToken).ConfigureAwait(false);
+                    cases.AddRange(list.List);
+                }
+                catch (Exception ex)
+                {
+                    _logger.Warning(ex, "MatchingService: failed to list cases for {ContactId}", contact.Id);
+                }
+
+                var result = new MatchResult
+                {
+                    SenderEmail = senderEmail,
+                    Contact = contact,
+                    Account = account,
+                    RecentCases = cases,
+                    CandidateCount = 1
+                };
+
+                _cache.Set<MatchResult?>(key, result, CacheExpiry);
+                return result;
+            }
+            catch (EspoCrmAuthorizationException)
+            {
+                throw;
+            }
+            catch (OperationCanceledException)
+            {
+                throw;
+            }
+            catch (Exception ex)
+            {
+                _logger.Warning(ex, "MatchingService lookup failed for {Email}", senderEmail);
+                return null;
+            }
+        }
+
+        public void Invalidate(string senderEmail)
+        {
+            if (string.IsNullOrWhiteSpace(senderEmail)) return;
+            _cache.Remove(CacheKey(senderEmail));
+        }
+
+        private static string CacheKey(string senderEmail)
+            => "match:" + senderEmail.Trim().ToLowerInvariant();
+    }
+}
diff --git a/src/OutlookAddin.UI/ViewModels/ReadingPaneViewModel.cs b/src/OutlookAddin.UI/ViewModels/ReadingPaneViewModel.cs
new file mode 100644
index 0000000..a8143fe
--- /dev/null
+++ b/src/OutlookAddin.UI/ViewModels/ReadingPaneViewModel.cs
@@ -0,0 +1,223 @@
+using System;
+using System.Collections.ObjectModel;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Windows;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using MarcusLaw.OutlookAddin.Core.Models;
+using MarcusLaw.OutlookAddin.Core.Services;
+using Serilog;
+
+namespace MarcusLaw.OutlookAddin.UI.ViewModels
+{
+    /// <summary>
+    /// Possible states of the sidebar. Each maps to a Visibility binding
+    /// in <c>ReadingPaneView.xaml</c>.
+    /// </summary>
+    public enum ReadingPaneState
+    {
+        Empty,
+        Loading,
+        Match,
+        NoMatch,
+        Ambiguous,
+        Error
+    }
+
+    public sealed partial class ReadingPaneViewModel : ObservableObject
+    {
+        private readonly IMatchingService _matchingService;
+        private readonly ILogger _logger;
+        private CancellationTokenSource? _activeLookup;
+
+        [ObservableProperty]
+        private ReadingPaneState state = ReadingPaneState.Empty;
+
+        [ObservableProperty]
+        private string senderEmail = string.Empty;
+
+        [ObservableProperty]
+        private MatchResult? match;
+
+        [ObservableProperty]
+        private string? errorMessage;
+
+        [ObservableProperty]
+        private string? ambiguousMessage;
+
+        [ObservableProperty]
+        private string? espoCrmBaseUrl;
+
+        public ObservableCollection<CaseEntity> RecentCases { get; } = new ObservableCollection<CaseEntity>();
+
+        public Visibility EmptyVisibility => Vis(State == ReadingPaneState.Empty);
+        public Visibility LoadingVisibility => Vis(State == ReadingPaneState.Loading);
+        public Visibility MatchVisibility => Vis(State == ReadingPaneState.Match);
+        public Visibility NoMatchVisibility => Vis(State == ReadingPaneState.NoMatch);
+        public Visibility AmbiguousVisibility => Vis(State == ReadingPaneState.Ambiguous);
+        public Visibility ErrorVisibility => Vis(State == ReadingPaneState.Error);
+        public Visibility AccountVisibility => Vis(Match?.Account != null);
+        public Visibility NoCasesVisibility => Vis(State == ReadingPaneState.Match && RecentCases.Count == 0);
+        public Visibility ActionsVisibility => Vis(State == ReadingPaneState.Match);
+
+        /// <summary>
+        /// Raised when the user clicks "File to this case" (carries the chosen
+        /// MatchResult.Contact / RecentCases pick) or "File elsewhere" (null).
+        /// Host wires this to <c>AddInHost.LaunchFileToCaseAsync</c>.
+        /// </summary>
+        public event EventHandler<FileFromSidebarEventArgs>? FileRequested;
+
+        /// <summary>
+        /// Raised when the user clicks "Open in EspoCRM". The host opens the URL.
+        /// </summary>
+        public event EventHandler<string>? OpenInBrowserRequested;
+
+        public ReadingPaneViewModel(IMatchingService matchingService, ILogger logger)
+        {
+            _matchingService = matchingService ?? throw new ArgumentNullException(nameof(matchingService));
+            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+        }
+
+        partial void OnStateChanged(ReadingPaneState value)
+        {
+            OnPropertyChanged(nameof(EmptyVisibility));
+            OnPropertyChanged(nameof(LoadingVisibility));
+            OnPropertyChanged(nameof(MatchVisibility));
+            OnPropertyChanged(nameof(NoMatchVisibility));
+            OnPropertyChanged(nameof(AmbiguousVisibility));
+            OnPropertyChanged(nameof(ErrorVisibility));
+            OnPropertyChanged(nameof(ActionsVisibility));
+            OnPropertyChanged(nameof(NoCasesVisibility));
+            FileToThisCommand.NotifyCanExecuteChanged();
+            FileElsewhereCommand.NotifyCanExecuteChanged();
+            OpenInEspoCrmCommand.NotifyCanExecuteChanged();
+        }
+
+        partial void OnMatchChanged(MatchResult? value)
+        {
+            RecentCases.Clear();
+            if (value?.RecentCases != null)
+            {
+                foreach (var c in value.RecentCases) RecentCases.Add(c);
+            }
+            OnPropertyChanged(nameof(AccountVisibility));
+            OnPropertyChanged(nameof(NoCasesVisibility));
+        }
+
+        public void Reset()
+        {
+            CancelInFlight();
+            SenderEmail = string.Empty;
+            Match = null;
+            ErrorMessage = null;
+            AmbiguousMessage = null;
+            State = ReadingPaneState.Empty;
+        }
+
+        public async Task LoadAsync(string senderEmail)
+        {
+            CancelInFlight();
+            if (string.IsNullOrWhiteSpace(senderEmail))
+            {
+                Reset();
+                return;
+            }
+
+            SenderEmail = senderEmail;
+            State = ReadingPaneState.Loading;
+
+            var cts = new CancellationTokenSource();
+            _activeLookup = cts;
+
+            try
+            {
+                var result = await _matchingService.LookupAsync(senderEmail, cts.Token).ConfigureAwait(true);
+                if (cts.IsCancellationRequested) return;
+
+                if (result == null)
+                {
+                    Match = null;
+                    State = ReadingPaneState.NoMatch;
+                    return;
+                }
+
+                if (result.IsAmbiguous)
+                {
+                    Match = result;
+                    AmbiguousMessage = $"נמצאו {result.CandidateCount} אנשי קשר עם הכתובת הזו — נדרשת בחירה ידנית.";
+                    State = ReadingPaneState.Ambiguous;
+                    return;
+                }
+
+                Match = result;
+                State = ReadingPaneState.Match;
+            }
+            catch (OperationCanceledException)
+            {
+                // Selection changed before lookup finished — ignore.
+            }
+            catch (EspoCrmAuthorizationException)
+            {
+                ErrorMessage = "מפתח ה-API נדחה. עדכן בהגדרות.";
+                State = ReadingPaneState.Error;
+            }
+            catch (Exception ex)
+            {
+                _logger.Warning(ex, "ReadingPaneViewModel.LoadAsync failed for {Email}", senderEmail);
+                ErrorMessage = "שגיאת התחברות לשרת.";
+                State = ReadingPaneState.Error;
+            }
+        }
+
+        private void CancelInFlight()
+        {
+            try { _activeLookup?.Cancel(); } catch { /* ignore */ }
+            _activeLookup = null;
+        }
+
+        [RelayCommand(CanExecute = nameof(CanFileToThis))]
+        private void FileToThis()
+        {
+            FileRequested?.Invoke(this, new FileFromSidebarEventArgs(Match!));
+        }
+
+        private bool CanFileToThis() => State == ReadingPaneState.Match && Match?.Contact != null;
+
+        [RelayCommand(CanExecute = nameof(CanFileElsewhere))]
+        private void FileElsewhere()
+        {
+            FileRequested?.Invoke(this, new FileFromSidebarEventArgs(null));
+        }
+
+        private bool CanFileElsewhere() => true;
+
+        [RelayCommand(CanExecute = nameof(CanOpenInCrm))]
+        private void OpenInEspoCrm()
+        {
+            if (string.IsNullOrWhiteSpace(EspoCrmBaseUrl) || Match?.Contact == null) return;
+            var url = EspoCrmBaseUrl!.TrimEnd('/') + "/#Contact/view/" + Match.Contact.Id;
+            OpenInBrowserRequested?.Invoke(this, url);
+        }
+
+        private bool CanOpenInCrm() => State == ReadingPaneState.Match && Match?.Contact != null;
+
+        [RelayCommand]
+        private void OpenManualSearch()
+        {
+            FileRequested?.Invoke(this, new FileFromSidebarEventArgs(null));
+        }
+
+        private static Visibility Vis(bool show) => show ? Visibility.Visible : Visibility.Collapsed;
+    }
+
+    public sealed class FileFromSidebarEventArgs : EventArgs
+    {
+        public MatchResult? PreselectedMatch { get; }
+
+        public FileFromSidebarEventArgs(MatchResult? preselected)
+        {
+            PreselectedMatch = preselected;
+        }
+    }
+}
diff --git a/src/OutlookAddin.UI/Views/ReadingPaneView.xaml b/src/OutlookAddin.UI/Views/ReadingPaneView.xaml
new file mode 100644
index 0000000..239b5e2
--- /dev/null
+++ b/src/OutlookAddin.UI/Views/ReadingPaneView.xaml
@@ -0,0 +1,121 @@
+<UserControl x:Class="MarcusLaw.OutlookAddin.UI.Views.ReadingPaneView"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             FlowDirection="RightToLeft"
+             Background="White"
+             FontFamily="Segoe UI"
+             FontSize="12">
+    <UserControl.Resources>
+        <Style TargetType="TextBlock">
+            <Setter Property="TextWrapping" Value="Wrap" />
+        </Style>
+        <Style x:Key="LabelStyle" TargetType="TextBlock">
+            <Setter Property="Foreground" Value="Gray" />
+            <Setter Property="FontSize" Value="10" />
+            <Setter Property="Margin" Value="0,4,0,2" />
+        </Style>
+        <Style x:Key="LinkButtonStyle" TargetType="Button">
+            <Setter Property="Background" Value="Transparent" />
+            <Setter Property="BorderThickness" Value="0" />
+            <Setter Property="Foreground" Value="#0066CC" />
+            <Setter Property="Padding" Value="0" />
+            <Setter Property="Cursor" Value="Hand" />
+            <Setter Property="HorizontalAlignment" Value="Right" />
+        </Style>
+    </UserControl.Resources>
+
+    <Grid Margin="10">
+        <Grid.RowDefinitions>
+            <RowDefinition Height="Auto" />
+            <RowDefinition Height="*" />
+            <RowDefinition Height="Auto" />
+        </Grid.RowDefinitions>
+
+        <TextBlock Grid.Row="0" Text="פרטי תיק" FontWeight="Bold" FontSize="14" Margin="0,0,0,8" />
+
+        <ScrollViewer Grid.Row="1" VerticalScrollBarVisibility="Auto">
+            <Grid>
+                <!-- Loading -->
+                <StackPanel Visibility="{Binding LoadingVisibility}" HorizontalAlignment="Center" VerticalAlignment="Center">
+                    <ProgressBar IsIndeterminate="True" Width="120" Height="6" Margin="0,0,0,8" />
+                    <TextBlock Text="טוען…" Foreground="Gray" HorizontalAlignment="Center" />
+                </StackPanel>
+
+                <!-- Empty / no selection -->
+                <TextBlock Visibility="{Binding EmptyVisibility}"
+                           Text="סמן מייל כדי לראות את פרטי התיק"
+                           Foreground="Gray" HorizontalAlignment="Center" VerticalAlignment="Center"
+                           TextAlignment="Center" />
+
+                <!-- No match -->
+                <StackPanel Visibility="{Binding NoMatchVisibility}">
+                    <TextBlock Text="לא נמצא איש קשר ל-" Foreground="Gray" />
+                    <TextBlock Text="{Binding SenderEmail}" FontWeight="Bold" />
+                    <Button Content="חפש ידנית ב-EspoCRM"
+                            Command="{Binding OpenManualSearchCommand}"
+                            Style="{StaticResource LinkButtonStyle}"
+                            Margin="0,12,0,0" />
+                </StackPanel>
+
+                <!-- Ambiguous -->
+                <StackPanel Visibility="{Binding AmbiguousVisibility}">
+                    <TextBlock Text="{Binding AmbiguousMessage}" Foreground="DarkOrange" />
+                    <Button Content="פתח חיפוש ידני"
+                            Command="{Binding OpenManualSearchCommand}"
+                            Style="{StaticResource LinkButtonStyle}"
+                            Margin="0,12,0,0" />
+                </StackPanel>
+
+                <!-- Match -->
+                <StackPanel Visibility="{Binding MatchVisibility}">
+                    <TextBlock Style="{StaticResource LabelStyle}" Text="איש קשר" />
+                    <TextBlock Text="{Binding Match.Contact.Name}" FontSize="14" FontWeight="Bold" />
+                    <TextBlock Text="{Binding Match.Contact.EmailAddress}" Foreground="Gray" />
+
+                    <TextBlock Style="{StaticResource LabelStyle}" Text="לקוח/חברה" Visibility="{Binding AccountVisibility}" />
+                    <TextBlock Text="{Binding Match.Account.Name}" Visibility="{Binding AccountVisibility}" />
+
+                    <TextBlock Style="{StaticResource LabelStyle}" Text="תיקים אחרונים" Margin="0,12,0,2" />
+                    <ItemsControl ItemsSource="{Binding RecentCases}">
+                        <ItemsControl.ItemTemplate>
+                            <DataTemplate>
+                                <Border BorderBrush="#EEE" BorderThickness="0,0,0,1" Padding="0,4">
+                                    <StackPanel>
+                                        <TextBlock>
+                                            <Run Text="["/><Run Text="{Binding Number, Mode=OneWay}"/><Run Text="] " />
+                                            <Run Text="{Binding Name, Mode=OneWay}" FontWeight="SemiBold" />
+                                        </TextBlock>
+                                        <TextBlock Text="{Binding Status}" Foreground="Gray" FontSize="10" />
+                                    </StackPanel>
+                                </Border>
+                            </DataTemplate>
+                        </ItemsControl.ItemTemplate>
+                    </ItemsControl>
+
+                    <TextBlock Text="(אין תיקים פתוחים)" Foreground="Gray" FontStyle="Italic"
+                               Visibility="{Binding NoCasesVisibility}" Margin="0,4,0,0" />
+                </StackPanel>
+
+                <!-- Error -->
+                <TextBlock Visibility="{Binding ErrorVisibility}"
+                           Text="{Binding ErrorMessage}"
+                           Foreground="Firebrick" TextWrapping="Wrap" />
+            </Grid>
+        </ScrollViewer>
+
+        <StackPanel Grid.Row="2" Margin="0,8,0,0" Visibility="{Binding ActionsVisibility}">
+            <Button Content="תייק לתיק הזה"
+                    Command="{Binding FileToThisCommand}"
+                    Padding="8,4" Margin="0,0,0,4"
+                    HorizontalAlignment="Stretch" />
+            <Button Content="תייק למקום אחר…"
+                    Command="{Binding FileElsewhereCommand}"
+                    Padding="8,4" Margin="0,0,0,4"
+                    HorizontalAlignment="Stretch" />
+            <Button Content="פתח ב-EspoCRM"
+                    Command="{Binding OpenInEspoCrmCommand}"
+                    Padding="8,4"
+                    HorizontalAlignment="Stretch" />
+        </StackPanel>
+    </Grid>
+</UserControl>
diff --git a/src/OutlookAddin.UI/Views/ReadingPaneView.xaml.cs b/src/OutlookAddin.UI/Views/ReadingPaneView.xaml.cs
new file mode 100644
index 0000000..4ba857b
--- /dev/null
+++ b/src/OutlookAddin.UI/Views/ReadingPaneView.xaml.cs
@@ -0,0 +1,12 @@
+using System.Windows.Controls;
+
+namespace MarcusLaw.OutlookAddin.UI.Views
+{
+    public partial class ReadingPaneView : UserControl
+    {
+        public ReadingPaneView()
+        {
+            InitializeComponent();
+        }
+    }
+}
diff --git a/src/OutlookAddin/OutlookAddin.csproj b/src/OutlookAddin/OutlookAddin.csproj
index 9bfdd45..185f46d 100644
--- a/src/OutlookAddin/OutlookAddin.csproj
+++ b/src/OutlookAddin/OutlookAddin.csproj
@@ -116,6 +116,7 @@
     <Reference Include="PresentationCore" />
     <Reference Include="PresentationFramework" />
     <Reference Include="WindowsBase" />
+    <Reference Include="WindowsFormsIntegration" />
     <Reference Include="System.Xaml" />
   </ItemGroup>
   <ItemGroup>
@@ -234,12 +235,18 @@
     <Compile Include="Services\AddInHost.cs">
       <SubType>Code</SubType>
     </Compile>
+    <Compile Include="Services\ExplorerSelectionHandler.cs">
+      <SubType>Code</SubType>
+    </Compile>
     <Compile Include="Services\MailItemExtractor.cs">
       <SubType>Code</SubType>
     </Compile>
     <Compile Include="Services\RetryQueueProcessor.cs">
       <SubType>Code</SubType>
     </Compile>
+    <Compile Include="Services\SidebarController.cs">
+      <SubType>Code</SubType>
+    </Compile>
     <AppDesigner Include="Properties\" />
   </ItemGroup>
   <ItemGroup>
diff --git a/src/OutlookAddin/Services/AddInHost.cs b/src/OutlookAddin/Services/AddInHost.cs
index 2d70e78..93031c9 100644
--- a/src/OutlookAddin/Services/AddInHost.cs
+++ b/src/OutlookAddin/Services/AddInHost.cs
@@ -12,6 +12,8 @@ using MarcusLaw.OutlookAddin.Core.Security;
 using MarcusLaw.OutlookAddin.Core.Services;
 using MarcusLaw.OutlookAddin.UI.Dialogs;
 using MarcusLaw.OutlookAddin.UI.ViewModels;
+using Microsoft.Extensions.Caching.Memory;
+using Microsoft.Office.Tools;
 using Serilog;
 using Outlook = Microsoft.Office.Interop.Outlook;
 
@@ -34,10 +36,13 @@ namespace OutlookAddin.Services
 
         public IEspoCrmClient? CrmClient { get; private set; }
         public IFilingService? FilingService { get; private set; }
+        public IMatchingService? MatchingService { get; private set; }
 
         private readonly Outlook.Application _outlookApp;
+        private readonly MemoryCache _matchCache = new MemoryCache(new MemoryCacheOptions());
         private RetryQueueProcessor? _retryProcessor;
         private HttpClient? _httpClient;
+        private SidebarController? _sidebarController;
 
         public AddInHost(Outlook.Application outlookApp)
         {
@@ -53,6 +58,56 @@ namespace OutlookAddin.Services
             TryInitializeCrm();
         }
 
+        /// <summary>
+        /// Called by ThisAddIn_Startup once the VSTO task-pane collection is
+        /// available. Spawns the right-hand "Case Info" pane on every Explorer.
+        /// </summary>
+        public void InitializeSidebar(CustomTaskPaneCollection taskPanes)
+        {
+            if (taskPanes == null) throw new ArgumentNullException(nameof(taskPanes));
+            if (_sidebarController != null) return;
+
+            if (MatchingService == null)
+            {
+                Logger.Information("AddInHost: sidebar deferred — MatchingService not yet available");
+                CrmClientChanged += OnCrmClientChangedForSidebar;
+                _pendingTaskPanes = taskPanes;
+                return;
+            }
+
+            StartSidebar(taskPanes);
+        }
+
+        private CustomTaskPaneCollection? _pendingTaskPanes;
+
+        private void OnCrmClientChangedForSidebar(object? sender, EventArgs e)
+        {
+            if (MatchingService == null || _pendingTaskPanes == null || _sidebarController != null) return;
+            StartSidebar(_pendingTaskPanes);
+            CrmClientChanged -= OnCrmClientChangedForSidebar;
+            _pendingTaskPanes = null;
+        }
+
+        private void StartSidebar(CustomTaskPaneCollection taskPanes)
+        {
+            try
+            {
+                _sidebarController = new SidebarController(
+                    taskPanes,
+                    _outlookApp,
+                    MatchingService!,
+                    this,
+                    System.Windows.Threading.Dispatcher.CurrentDispatcher,
+                    Logger);
+                _sidebarController.Initialize();
+                Logger.Information("AddInHost: sidebar attached");
+            }
+            catch (Exception ex)
+            {
+                Logger.Error(ex, "AddInHost: sidebar attach failed");
+            }
+        }
+
         public bool IsConfigured => CrmClient != null && FilingService != null;
 
         public event EventHandler? CrmClientChanged;
@@ -81,6 +136,7 @@ namespace OutlookAddin.Services
                 _httpClient = new HttpClient { Timeout = TimeSpan.FromSeconds(30) };
                 CrmClient = new EspoCrmClient(_httpClient, baseUrl.ToString(), creds.Username, creds.ApiKey, Logger);
                 FilingService = new FilingService(CrmClient, RetryQueue, Logger);
+                MatchingService = new MatchingService(CrmClient, _matchCache, Logger);
                 _retryProcessor = new RetryQueueProcessor(RetryQueue, CrmClient, Logger);
                 _retryProcessor.Start();
                 Logger.Information("AddInHost: CRM client initialized for {BaseUrl}", baseUrl);
@@ -102,6 +158,7 @@ namespace OutlookAddin.Services
             _httpClient = null;
             CrmClient = null;
             FilingService = null;
+            MatchingService = null;
         }
 
         /// <summary>
@@ -362,8 +419,10 @@ namespace OutlookAddin.Services
 
         public void Dispose()
         {
+            try { _sidebarController?.Dispose(); } catch { }
             try { _retryProcessor?.Dispose(); } catch { }
             try { _httpClient?.Dispose(); } catch { }
+            try { _matchCache.Dispose(); } catch { }
             try
             {
                 Logger.Information("AddInHost shutting down");
diff --git a/src/OutlookAddin/Services/ExplorerSelectionHandler.cs b/src/OutlookAddin/Services/ExplorerSelectionHandler.cs
new file mode 100644
index 0000000..a5e4140
--- /dev/null
+++ b/src/OutlookAddin/Services/ExplorerSelectionHandler.cs
@@ -0,0 +1,143 @@
+using System;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Windows.Threading;
+using MarcusLaw.OutlookAddin.UI.ViewModels;
+using Serilog;
+using Outlook = Microsoft.Office.Interop.Outlook;
+
+namespace OutlookAddin.Services
+{
+    /// <summary>
+    /// Subscribes to <see cref="Outlook.Explorer.SelectionChange"/>, debounces
+    /// the storm of events Outlook fires while the user is scrolling
+    /// (typically every ~30ms), and forwards the resulting sender-email
+    /// lookup to the <see cref="ReadingPaneViewModel"/>.
+    /// </summary>
+    public sealed class ExplorerSelectionHandler : IDisposable
+    {
+        public TimeSpan DebounceInterval { get; }
+
+        private readonly Outlook.Explorer _explorer;
+        private readonly ReadingPaneViewModel _viewModel;
+        private readonly Dispatcher _dispatcher;
+        private readonly ILogger _logger;
+        private readonly Timer _timer;
+        private string? _lastSenderEmail;
+        private int _disposed;
+
+        public ExplorerSelectionHandler(
+            Outlook.Explorer explorer,
+            ReadingPaneViewModel viewModel,
+            Dispatcher dispatcher,
+            ILogger logger,
+            TimeSpan? debounce = null)
+        {
+            _explorer = explorer ?? throw new ArgumentNullException(nameof(explorer));
+            _viewModel = viewModel ?? throw new ArgumentNullException(nameof(viewModel));
+            _dispatcher = dispatcher ?? throw new ArgumentNullException(nameof(dispatcher));
+            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+            DebounceInterval = debounce ?? TimeSpan.FromMilliseconds(200);
+
+            _timer = new Timer(OnTimerFired, null, Timeout.Infinite, Timeout.Infinite);
+            _explorer.SelectionChange += OnSelectionChange;
+        }
+
+        public void TriggerNow()
+        {
+            OnSelectionChange();
+        }
+
+        private void OnSelectionChange()
+        {
+            if (Volatile.Read(ref _disposed) != 0) return;
+            try
+            {
+                _timer.Change(DebounceInterval, Timeout.InfiniteTimeSpan);
+            }
+            catch (ObjectDisposedException) { }
+        }
+
+        private void OnTimerFired(object? state)
+        {
+            if (Volatile.Read(ref _disposed) != 0) return;
+            try
+            {
+                _dispatcher.BeginInvoke((Action)ProcessOnUiThread);
+            }
+            catch (Exception ex)
+            {
+                _logger.Warning(ex, "ExplorerSelectionHandler: dispatcher invoke failed");
+            }
+        }
+
+        private void ProcessOnUiThread()
+        {
+            string? senderEmail = ReadSelectedSenderEmail();
+
+            // Only kick a lookup when the sender has actually changed; otherwise
+            // we'd hammer the cache for every keyboard arrow press on the same row.
+            if (string.Equals(senderEmail, _lastSenderEmail, StringComparison.OrdinalIgnoreCase)) return;
+            _lastSenderEmail = senderEmail;
+
+            if (string.IsNullOrWhiteSpace(senderEmail))
+            {
+                _viewModel.Reset();
+                return;
+            }
+
+            _ = _viewModel.LoadAsync(senderEmail);
+        }
+
+        private string? ReadSelectedSenderEmail()
+        {
+            Outlook.Selection? selection = null;
+            object? entry = null;
+            try
+            {
+                selection = _explorer.Selection;
+                if (selection == null || selection.Count == 0) return null;
+                entry = selection[1];
+                if (entry is Outlook.MailItem mail)
+                {
+                    var smtp = SafeGet(() => mail.SenderEmailAddress);
+                    if (!string.IsNullOrWhiteSpace(smtp) && smtp.Contains("@"))
+                    {
+                        return smtp;
+                    }
+                }
+                return null;
+            }
+            catch (Exception ex)
+            {
+                _logger.Warning(ex, "ExplorerSelectionHandler: ReadSelectedSenderEmail failed");
+                return null;
+            }
+            finally
+            {
+                Release(entry);
+                Release(selection);
+            }
+        }
+
+        private static T? SafeGet<T>(Func<T> getter) where T : class
+        {
+            try { return getter(); } catch { return null; }
+        }
+
+        private static void Release(object? com)
+        {
+            if (com != null && Marshal.IsComObject(com))
+            {
+                try { Marshal.ReleaseComObject(com); } catch { /* ignore */ }
+            }
+        }
+
+        public void Dispose()
+        {
+            if (Interlocked.Exchange(ref _disposed, 1) != 0) return;
+            try { _explorer.SelectionChange -= OnSelectionChange; } catch { /* ignore */ }
+            try { _timer.Dispose(); } catch { /* ignore */ }
+        }
+    }
+}
diff --git a/src/OutlookAddin/Services/SidebarController.cs b/src/OutlookAddin/Services/SidebarController.cs
new file mode 100644
index 0000000..7a2118d
--- /dev/null
+++ b/src/OutlookAddin/Services/SidebarController.cs
@@ -0,0 +1,201 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Windows.Forms.Integration;
+using System.Windows.Threading;
+using MarcusLaw.OutlookAddin.Core.Services;
+using MarcusLaw.OutlookAddin.UI.ViewModels;
+using MarcusLaw.OutlookAddin.UI.Views;
+using Microsoft.Office.Tools;
+using Serilog;
+using Office = Microsoft.Office.Core;
+using Outlook = Microsoft.Office.Interop.Outlook;
+
+namespace OutlookAddin.Services
+{
+    /// <summary>
+    /// Owns the per-Explorer "Case Info" task pane. For each active Explorer
+    /// window we host a single <see cref="ReadingPaneView"/> wrapped in
+    /// <see cref="ElementHost"/> and a <see cref="ExplorerSelectionHandler"/>
+    /// that drives lookups.
+    /// </summary>
+    public sealed class SidebarController : IDisposable
+    {
+        private const string PaneTitle = "פרטי תיק (EspoCRM)";
+        private const int DefaultWidth = 320;
+
+        private readonly CustomTaskPaneCollection _taskPanes;
+        private readonly Outlook.Application _app;
+        private readonly IMatchingService _matchingService;
+        private readonly AddInHost _host;
+        private readonly Dispatcher _dispatcher;
+        private readonly ILogger _logger;
+
+        private readonly Dictionary<int, ExplorerBinding> _bindings = new Dictionary<int, ExplorerBinding>();
+        private Outlook.Explorers? _explorers;
+
+        public SidebarController(
+            CustomTaskPaneCollection taskPanes,
+            Outlook.Application app,
+            IMatchingService matchingService,
+            AddInHost host,
+            Dispatcher dispatcher,
+            ILogger logger)
+        {
+            _taskPanes = taskPanes ?? throw new ArgumentNullException(nameof(taskPanes));
+            _app = app ?? throw new ArgumentNullException(nameof(app));
+            _matchingService = matchingService ?? throw new ArgumentNullException(nameof(matchingService));
+            _host = host ?? throw new ArgumentNullException(nameof(host));
+            _dispatcher = dispatcher ?? throw new ArgumentNullException(nameof(dispatcher));
+            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+        }
+
+        public void Initialize()
+        {
+            try
+            {
+                _explorers = _app.Explorers;
+                _explorers.NewExplorer += OnNewExplorer;
+
+                // Attach to whatever Explorer is open right now.
+                var active = _app.ActiveExplorer();
+                if (active != null)
+                {
+                    AttachToExplorer(active);
+                }
+            }
+            catch (Exception ex)
+            {
+                _logger.Error(ex, "SidebarController.Initialize failed");
+            }
+        }
+
+        private void OnNewExplorer(Outlook.Explorer explorer)
+        {
+            try { AttachToExplorer(explorer); }
+            catch (Exception ex) { _logger.Warning(ex, "SidebarController.OnNewExplorer failed"); }
+        }
+
+        private void AttachToExplorer(Outlook.Explorer explorer)
+        {
+            var key = ExplorerKey(explorer);
+            if (_bindings.ContainsKey(key)) return;
+
+            var view = new ReadingPaneView();
+            var vm = new ReadingPaneViewModel(_matchingService, _logger)
+            {
+                EspoCrmBaseUrl = _host.Settings.EspoCrmUrl
+            };
+            view.DataContext = vm;
+
+            var element = new ElementHost
+            {
+                Child = view,
+                Dock = System.Windows.Forms.DockStyle.Fill
+            };
+
+            var pane = _taskPanes.Add(element, PaneTitle, explorer);
+            pane.DockPosition = Office.MsoCTPDockPosition.msoCTPDockPositionRight;
+            pane.Width = DefaultWidth;
+            pane.Visible = true;
+
+            var handler = new ExplorerSelectionHandler(explorer, vm, _dispatcher, _logger);
+
+            vm.FileRequested += async (s, e) =>
+            {
+                try { await _host.LaunchFileToCaseAsync().ConfigureAwait(true); }
+                catch (Exception ex) { _logger.Warning(ex, "Sidebar file-request handler failed"); }
+            };
+            vm.OpenInBrowserRequested += (s, url) => TryOpenInBrowser(url);
+
+            explorer.Close += () => DetachExplorer(key);
+
+            _bindings[key] = new ExplorerBinding(pane, element, vm, handler, explorer);
+
+            // Kick a first lookup based on whatever is selected when the pane opens.
+            handler.TriggerNow();
+        }
+
+        private void DetachExplorer(int key)
+        {
+            if (!_bindings.TryGetValue(key, out var binding)) return;
+            _bindings.Remove(key);
+            binding.Dispose();
+        }
+
+        private static int ExplorerKey(Outlook.Explorer explorer)
+        {
+            // RuntimeCallableWrapper identity is unstable across RCW reads,
+            // but the underlying COM pointer is stable; use it as the dictionary key.
+            var ptr = Marshal.GetIUnknownForObject(explorer);
+            try { return ptr.GetHashCode(); }
+            finally { Marshal.Release(ptr); }
+        }
+
+        private void TryOpenInBrowser(string url)
+        {
+            try
+            {
+                Process.Start(new ProcessStartInfo
+                {
+                    FileName = url,
+                    UseShellExecute = true
+                });
+            }
+            catch (Exception ex)
+            {
+                _logger.Warning(ex, "TryOpenInBrowser failed for {Url}", url);
+            }
+        }
+
+        public void Dispose()
+        {
+            try
+            {
+                if (_explorers != null)
+                {
+                    _explorers.NewExplorer -= OnNewExplorer;
+                }
+            }
+            catch { /* ignore */ }
+
+            foreach (var binding in _bindings.Values)
+            {
+                binding.Dispose();
+            }
+            _bindings.Clear();
+        }
+
+        private sealed class ExplorerBinding : IDisposable
+        {
+            private readonly CustomTaskPane _pane;
+            private readonly ElementHost _element;
+            private readonly ExplorerSelectionHandler _handler;
+            private readonly Outlook.Explorer _explorer;
+
+            public ReadingPaneViewModel ViewModel { get; }
+
+            public ExplorerBinding(
+                CustomTaskPane pane,
+                ElementHost element,
+                ReadingPaneViewModel viewModel,
+                ExplorerSelectionHandler handler,
+                Outlook.Explorer explorer)
+            {
+                _pane = pane;
+                _element = element;
+                ViewModel = viewModel;
+                _handler = handler;
+                _explorer = explorer;
+            }
+
+            public void Dispose()
+            {
+                try { _handler.Dispose(); } catch { /* ignore */ }
+                try { _pane.Visible = false; } catch { /* ignore */ }
+                try { _element.Dispose(); } catch { /* ignore */ }
+            }
+        }
+    }
+}
diff --git a/src/OutlookAddin/ThisAddIn.cs b/src/OutlookAddin/ThisAddIn.cs
index 9138b95..2a053d9 100644
--- a/src/OutlookAddin/ThisAddIn.cs
+++ b/src/OutlookAddin/ThisAddIn.cs
@@ -14,6 +14,7 @@ namespace OutlookAddin
             try
             {
                 AddInHost = new AddInHost(this.Application);
+                AddInHost.InitializeSidebar(this.CustomTaskPanes);
             }
             catch (Exception ex)
             {