diff --git a/src/OutlookAddin.Core/Services/AttachmentSaveService.cs b/src/OutlookAddin.Core/Services/AttachmentSaveService.cs
index 3c5ccaa..9af7f5a 100644
--- a/src/OutlookAddin.Core/Services/AttachmentSaveService.cs
+++ b/src/OutlookAddin.Core/Services/AttachmentSaveService.cs
@@ -59,6 +59,12 @@ namespace MarcusLaw.OutlookAddin.Core.Services
                     await _client.UploadAttachmentToNetworkStorageAsync(
                         uploaded.Id, trimmedFolder, cancellationToken).ConfigureAwait(false);
 
+                    // Step 3: verify the file actually landed on the share —
+                    // the server can return 200 yet leave nothing on disk
+                    // when a downstream WebDAV proxy silently fails. Read
+                    // the folder back and look for our filename.
+                    await VerifyArrivedAsync(att.Name, trimmedFolder, cancellationToken).ConfigureAwait(false);
+
                     _logger.Information(
                         "Saved attachment {Name} → {Path} (attachmentId={AttachmentId})",
                         att.Name, trimmedFolder, uploaded.Id);
@@ -99,5 +105,54 @@ namespace MarcusLaw.OutlookAddin.Core.Services
 
             return summary;
         }
+
+        /// <summary>
+        /// Post-upload sanity check: list the folder we just wrote into
+        /// and confirm a file with the same (possibly sanitized) name
+        /// shows up. Diagnostic only — does not change the outcome. If
+        /// the file isn't there, log a WARNING with everything that IS
+        /// in the folder so we can spot the actual server-side path.
+        /// </summary>
+        private async Task VerifyArrivedAsync(string expectedName, string folderPath, CancellationToken ct)
+        {
+            try
+            {
+                var items = await _client.ListNetworkStorageFolderAsync(folderPath, ct).ConfigureAwait(false);
+                var trimmedExpected = expectedName.Trim().TrimStart('-', ' ').TrimEnd('-', ' ');
+                bool found = false;
+                foreach (var it in items)
+                {
+                    if (it.IsFolder) continue;
+                    if (string.Equals(it.Name, expectedName, StringComparison.Ordinal) ||
+                        string.Equals(it.Name, trimmedExpected, StringComparison.Ordinal))
+                    {
+                        found = true;
+                        break;
+                    }
+                }
+                if (!found)
+                {
+                    var names = new List<string>();
+                    foreach (var it in items)
+                    {
+                        if (it.IsFolder) continue;
+                        names.Add(it.Name);
+                    }
+                    _logger.Warning(
+                        "Post-upload verify: expected '{Expected}' under '{Path}' but it's NOT in the listing. " +
+                        "Server reported the upload as successful but the file is not on the share. " +
+                        "Files currently in that folder: [{Files}]",
+                        expectedName, folderPath, string.Join(", ", names));
+                }
+                else
+                {
+                    _logger.Information("Post-upload verify: '{Expected}' present under '{Path}'", expectedName, folderPath);
+                }
+            }
+            catch (Exception ex)
+            {
+                _logger.Warning(ex, "Post-upload verify failed for '{Expected}' under '{Path}'", expectedName, folderPath);
+            }
+        }
     }
 }