diff --git a/application/Espo/Services/AdminNotifications.php b/application/Espo/Services/AdminNotifications.php
index db3521bc10..8b7a73100d 100644
--- a/application/Espo/Services/AdminNotifications.php
+++ b/application/Espo/Services/AdminNotifications.php
@@ -41,9 +41,9 @@ class AdminNotifications implements
 {
     use Di\EntityManagerSetter;
 
-    protected $config;
+    private $config;
 
-    protected $configWriter;
+    private $configWriter;
 
     public function __construct(Config $config, ConfigWriter $configWriter)
     {
@@ -54,12 +54,12 @@ class AdminNotifications implements
     /**
      * Job for checking a new version of EspoCRM.
      */
-    public function jobCheckNewVersion()
+    public function jobCheckNewVersion(): void
     {
         $config = $this->config;
 
         if (!$config->get('adminNotifications') || !$config->get('adminNotificationsNewVersion')) {
-            return true;
+            return;
         }
 
         $latestRelease = $this->getLatestRelease();
@@ -69,7 +69,7 @@ class AdminNotifications implements
 
             $this->configWriter->save();
 
-            return true;
+            return;
         }
 
         if ($config->get('latestVersion') != $latestRelease['version']) {
@@ -81,25 +81,23 @@ class AdminNotifications implements
 
             $this->configWriter->save();
 
-            return true;
+            return;
         }
 
         if (!empty($latestRelease['notes'])) {
             // @todo Find and modify notification.
         }
-
-        return true;
     }
 
     /**
      * Job for checking a new version of installed extensions.
      */
-    public function jobCheckNewExtensionVersion()
+    public function jobCheckNewExtensionVersion(): void
     {
         $config = $this->config;
 
         if (!$config->get('adminNotifications') || !$config->get('adminNotificationsNewExtensionVersion')) {
-            return true;
+            return;
         }
 
         $query = $this->entityManager->getQueryBuilder()
@@ -136,7 +134,6 @@ class AdminNotifications implements
         $save = false;
 
         foreach ($latestReleases as $extensionName => $extensionData) {
-
             if (empty($latestExtensionVersions[$extensionName])) {
                 $latestExtensionVersions[$extensionName] = $extensionData['version'];
                 $save = true;
@@ -166,10 +163,12 @@ class AdminNotifications implements
 
             $this->configWriter->save();
         }
-
-        return true;
     }
 
+    /**
+     * @param array<string,mixed> $requestData
+     * @return ?array<mixed,mixed>
+     */
     protected function getLatestRelease(
         ?string $url = null,
         array $requestData = [],
diff --git a/application/Espo/Services/App.php b/application/Espo/Services/App.php
index ad0c13430a..dfbd8aa811 100644
--- a/application/Espo/Services/App.php
+++ b/application/Espo/Services/App.php
@@ -110,6 +110,9 @@ class App
         $this->log = $log;
     }
 
+    /**
+     * @return array<string,mixed>
+     */
     public function getUserData(): array
     {
         $preferencesData = $this->preferences->getValueMap();
@@ -161,6 +164,7 @@ class App
         ];
 
         foreach (($this->metadata->get(['app', 'appParams']) ?? []) as $paramKey => $item) {
+            /** @var ?class-string */
             $className = $item['className'] ?? null;
 
             if (!$className) {
@@ -190,7 +194,7 @@ class App
         ];
     }
 
-    private function getUserDataForFrontend()
+    private function getUserDataForFrontend(): stdClass
     {
         $user = $this->user;
 
@@ -230,7 +234,7 @@ class App
         return $data;
     }
 
-    private function getAclDataForFrontend()
+    private function getAclDataForFrontend(): stdClass
     {
         $data = $this->acl->getMapData();
 
@@ -251,7 +255,7 @@ class App
         return $data;
     }
 
-    private function getEmailAddressData()
+    private function getEmailAddressData(): stdClass
     {
         $user = $this->user;
 
@@ -337,6 +341,9 @@ class App
         ];
     }
 
+    /**
+     * @return int
+     */
     private function getMaxUploadSize()
     {
         $maxSize = 0;
@@ -391,20 +398,20 @@ class App
         return $value;
     }
 
-    public function jobClearCache()
+    public function jobClearCache(): void
     {
         $this->dataManager->clearCache();
     }
 
-    public function jobRebuild()
+    public function jobRebuild(): void
     {
         $this->dataManager->rebuild();
     }
 
     /**
-     * @todo Remove in 6.0.
+     * @todo Remove in 7.2.
      */
-    public function jobPopulatePhoneNumberNumeric()
+    public function jobPopulatePhoneNumberNumeric(): void
     {
         $numberList = $this->entityManager
             ->getRDBRepository('PhoneNumber')
@@ -416,9 +423,9 @@ class App
     }
 
     /**
-     * @todo Remove in 6.0. Move to another place. CLI command.
+     * @todo Remove in 7.2. Move to another place. CLI command.
      */
-    public function jobPopulateArrayValues()
+    public function jobPopulateArrayValues(): void
     {
         $scopeList = array_keys($this->metadata->get(['scopes']));
 
@@ -517,9 +524,9 @@ class App
     }
 
     /**
-     * @todo Remove in 6.0. Move to another place. CLI command.
+     * @todo Remove in 7.2. Move to another place. CLI command.
      */
-    public function jobPopulateOptedOutPhoneNumbers()
+    public function jobPopulateOptedOutPhoneNumbers(): void
     {
         $entityTypeList = ['Contact', 'Lead'];
 
@@ -553,7 +560,7 @@ class App
         }
     }
 
-    private function filterPreferencesData(stdClass $data)
+    private function filterPreferencesData(stdClass $data): void
     {
         $passwordFieldList = $this->fieldUtil->getFieldByTypeList('Preferences', 'password');
 
diff --git a/application/Espo/Services/Attachment.php b/application/Espo/Services/Attachment.php
index 6f298a58c9..27628d41c6 100644
--- a/application/Espo/Services/Attachment.php
+++ b/application/Espo/Services/Attachment.php
@@ -43,16 +43,31 @@ use stdClass;
 
 class Attachment extends Record
 {
+    /**
+     * @var string[]
+     */
     protected $notFilteringAttributeList = ['contents'];
 
+    /**
+     * @var string[]
+     */
     protected $attachmentFieldTypeList = ['file', 'image', 'attachmentMultiple'];
 
+    /**
+     * @var string[]
+     */
     protected $inlineAttachmentFieldTypeList = ['wysiwyg'];
 
+    /**
+     * @var string[]
+     */
     protected $adminOnlyHavingInlineAttachmentsEntityTypeList = [
         'TemplateManager',
     ];
 
+    /**
+     * @var string[]
+     */
     protected $imageTypeList = [
         'image/png',
         'image/jpeg',
@@ -60,6 +75,10 @@ class Attachment extends Record
         'image/webp',
     ];
 
+    /**
+     * @param string $fileData
+     * @throws Forbidden
+     */
     public function upload($fileData): Entity
     {
         if (!$this->getAcl()->checkScope('Attachment', 'create')) {
@@ -213,13 +232,11 @@ class Attachment extends Record
         }
     }
 
-    protected function checkAttachmentField($relatedEntityType, $field, $role = 'Attachment')
+    protected function checkAttachmentField(string $relatedEntityType, string $field, string $role = 'Attachment'): void
     {
         if (
-            $this->getUser()->isAdmin()
-            &&
-            $role === 'Inline Attachment'
-            &&
+            $this->getUser()->isAdmin() &&
+            $role === 'Inline Attachment' &&
             in_array($relatedEntityType, $this->adminOnlyHavingInlineAttachmentsEntityTypeList)
         ) {
             return;
diff --git a/application/Espo/Services/CurrencyRate.php b/application/Espo/Services/CurrencyRate.php
index 2304ba7f77..a9d7450844 100644
--- a/application/Espo/Services/CurrencyRate.php
+++ b/application/Espo/Services/CurrencyRate.php
@@ -41,17 +41,17 @@ use Espo\Core\{
     Acl,
 };
 
-use StdClass;
+use stdClass;
 
 class CurrencyRate
 {
-    protected $config;
+    private $config;
 
-    protected $configWriter;
+    private $configWriter;
 
-    protected $dataManager;
+    private $dataManager;
 
-    protected $acl;
+    private $acl;
 
     public function __construct(Config $config, ConfigWriter $configWriter, DataManager $dataManager, Acl $acl)
     {
@@ -61,7 +61,7 @@ class CurrencyRate
         $this->acl = $acl;
     }
 
-    public function get(): StdClass
+    public function get(): stdClass
     {
         if (!$this->acl->check('Currency')) {
             throw new Forbidden();
@@ -76,7 +76,7 @@ class CurrencyRate
         );
     }
 
-    public function set(StdClass $rates): StdClass
+    public function set(stdClass $rates): stdClass
     {
         if (!$this->acl->check('Currency')) {
             throw new Forbidden();
diff --git a/application/Espo/Services/DashboardTemplate.php b/application/Espo/Services/DashboardTemplate.php
index 0212044e53..399afa8f0d 100644
--- a/application/Espo/Services/DashboardTemplate.php
+++ b/application/Espo/Services/DashboardTemplate.php
@@ -38,7 +38,7 @@ use Espo\Entities\User;
 
 class DashboardTemplate extends Record
 {
-    protected function applyLayout(Entity $preferences, Entity $template, bool $append)
+    protected function applyLayout(Entity $preferences, Entity $template, bool $append): void
     {
         if (!$append) {
             $preferences->set([
@@ -87,6 +87,11 @@ class DashboardTemplate extends Record
         }
     }
 
+    /**
+     * @param string[] $userIdList
+     * @throws NotFound
+     * @throws Forbidden
+     */
     public function deployToUsers(string $id, array $userIdList, bool $append = false): void
     {
         $template = $this->getEntityManager()->getEntity('DashboardTemplate', $id);
diff --git a/application/Espo/Services/Email.php b/application/Espo/Services/Email.php
index 1291c965bd..82bad7122e 100644
--- a/application/Espo/Services/Email.php
+++ b/application/Espo/Services/Email.php
@@ -73,6 +73,9 @@ class Email extends Record implements
 
     protected $getEntityBeforeUpdate = true;
 
+    /**
+     * @var string[]
+     */
     protected $allowedForUpdateAttributeList = [
         'parentType',
         'parentId',
@@ -371,7 +374,10 @@ class Email extends Record implements
         }
     }
 
-    protected function applySmtpHandler(string $userId, string $emailAddress, array &$params)
+    /**
+     * @param array<string,mixed> $params
+     */
+    protected function applySmtpHandler(string $userId, string $emailAddress, array &$params): void
     {
         $userData = $this->getUserDataRepository()->getByUserId($userId);
 
@@ -488,7 +494,10 @@ class Email extends Record implements
         return $entity;
     }
 
-    public function markAsReadByIdList(array $idList, $userId = null)
+    /**
+     * @param string[] $idList
+     */
+    public function markAsReadByIdList(array $idList, ?string $userId = null): bool
     {
         foreach ($idList as $id) {
             $this->markAsRead($id, $userId);
@@ -497,7 +506,10 @@ class Email extends Record implements
         return true;
     }
 
-    public function markAsNotReadByIdList(array $idList, $userId = null)
+    /**
+     * @param string[] $idList
+     */
+    public function markAsNotReadByIdList(array $idList, ?string $userId = null): bool
     {
         foreach ($idList as $id) {
             $this->markAsNotRead($id, $userId);
@@ -506,7 +518,10 @@ class Email extends Record implements
         return true;
     }
 
-    public function markAsImportantByIdList(array $idList, $userId = null)
+    /**
+     * @param string[] $idList
+     */
+    public function markAsImportantByIdList(array $idList, ?string $userId = null): bool
     {
         foreach ($idList as $id) {
             $this->markAsImportant($id, $userId);
@@ -515,7 +530,10 @@ class Email extends Record implements
         return true;
     }
 
-    public function markAsNotImportantByIdList(array $idList, $userId = null)
+    /**
+     * @param string[] $idList
+     */
+    public function markAsNotImportantByIdList(array $idList, ?string $userId = null): bool
     {
         foreach ($idList as $id) {
             $this->markAsNotImportant($id, $userId);
@@ -524,7 +542,10 @@ class Email extends Record implements
         return true;
     }
 
-    public function moveToTrashByIdList(array $idList, $userId = null)
+    /**
+     * @param string[] $idList
+     */
+    public function moveToTrashByIdList(array $idList, ?string $userId = null): bool
     {
         foreach ($idList as $id) {
             $this->moveToTrash($id, $userId);
@@ -533,7 +554,10 @@ class Email extends Record implements
         return true;
     }
 
-    public function moveToFolderByIdList(array $idList, $folderId, $userId = null)
+    /**
+     * @param string[] $idList
+     */
+    public function moveToFolderByIdList(array $idList, ?string $folderId, ?string $userId = null): bool
     {
         foreach ($idList as $id) {
             $this->moveToFolder($id, $folderId, $userId);
@@ -542,7 +566,10 @@ class Email extends Record implements
         return true;
     }
 
-    public function retrieveFromTrashByIdList(array $idList, $userId = null)
+    /**
+     * @param string[] $idList
+     */
+    public function retrieveFromTrashByIdList(array $idList, ?string $userId = null): bool
     {
         foreach ($idList as $id) {
             $this->retrieveFromTrash($id, $userId);
@@ -551,7 +578,7 @@ class Email extends Record implements
         return true;
     }
 
-    public function markAllAsRead(?string $userId = null)
+    public function markAllAsRead(?string $userId = null): bool
     {
         $userId = $userId ?? $this->getUser()->getId();
 
@@ -584,7 +611,7 @@ class Email extends Record implements
         return true;
     }
 
-    public function markAsRead(string $id, ?string $userId = null)
+    public function markAsRead(string $id, ?string $userId = null): bool
     {
         $userId = $userId ?? $this->getUser()->getId();
 
@@ -605,7 +632,7 @@ class Email extends Record implements
         return true;
     }
 
-    public function markAsNotRead(string $id, ?string $userId = null)
+    public function markAsNotRead(string $id, ?string $userId = null): bool
     {
         $userId = $userId ?? $this->getUser()->getId();
 
@@ -624,7 +651,7 @@ class Email extends Record implements
         return true;
     }
 
-    public function markAsImportant(string $id, ?string $userId = null)
+    public function markAsImportant(string $id, ?string $userId = null): bool
     {
         $userId = $userId ?? $this->getUser()->getId();
 
@@ -643,7 +670,7 @@ class Email extends Record implements
         return true;
     }
 
-    public function markAsNotImportant(string $id, ?string $userId = null)
+    public function markAsNotImportant(string $id, ?string $userId = null): bool
     {
         $userId = $userId ?? $this->getUser()->getId();
 
@@ -662,7 +689,7 @@ class Email extends Record implements
         return true;
     }
 
-    public function moveToTrash(string $id, ?string $userId = null)
+    public function moveToTrash(string $id, ?string $userId = null): bool
     {
         $userId = $userId ?? $this->getUser()->getId();
 
@@ -683,7 +710,7 @@ class Email extends Record implements
         return true;
     }
 
-    public function retrieveFromTrash(string $id, ?string $userId = null)
+    public function retrieveFromTrash(string $id, ?string $userId = null): bool
     {
         $userId = $userId ?? $this->getUser()->getId();
 
@@ -702,7 +729,7 @@ class Email extends Record implements
         return true;
     }
 
-    public function markNotificationAsRead(string $id, string $userId)
+    public function markNotificationAsRead(string $id, string $userId): void
     {
         $update = $this->entityManager->getQueryBuilder()->update()
             ->in('Notification')
@@ -720,7 +747,7 @@ class Email extends Record implements
         $this->entityManager->getQueryExecutor()->execute($update);
     }
 
-    public function moveToFolder(string $id, ?string $folderId, ?string $userId = null)
+    public function moveToFolder(string $id, ?string $folderId, ?string $userId = null): bool
     {
         $userId = $userId ?? $this->getUser()->getId();
 
@@ -852,7 +879,11 @@ class Email extends Record implements
         ];
     }
 
-    public function sendTestEmail(array $data)
+    /**
+     * @param array<string,mixed> $data
+     * @throws Forbidden
+     */
+    public function sendTestEmail(array $data): bool
     {
         $smtpParams = $data;
 
diff --git a/application/Espo/Services/EmailAccount.php b/application/Espo/Services/EmailAccount.php
index 1c8bb86464..1dbb4b3fbb 100644
--- a/application/Espo/Services/EmailAccount.php
+++ b/application/Espo/Services/EmailAccount.php
@@ -127,6 +127,9 @@ class EmailAccount extends Record implements
         return $emailAccount;
     }
 
+    /**
+     * @return ?array<string,mixed>
+     */
     public function getSmtpParamsFromAccount(EmailAccountEntity $emailAccount): ?array
     {
         $smtpParams = [];
@@ -156,8 +159,12 @@ class EmailAccount extends Record implements
         return null;
     }
 
-    public function applySmtpHandler(EmailAccountEntity $emailAccount, array &$params)
+    /**
+     * @param array<string,mixed> $params
+     */
+    public function applySmtpHandler(EmailAccountEntity $emailAccount, array &$params): void
     {
+        /** @var ?class-string */
         $handlerClassName = $emailAccount->get('smtpHandler');
 
         if (!$handlerClassName) {