diff --git a/tests/tine20/Admin/Frontend/Json/UserTest.php b/tests/tine20/Admin/Frontend/Json/UserTest.php
index eb945ea14a..3be2d50625 100644
--- a/tests/tine20/Admin/Frontend/Json/UserTest.php
+++ b/tests/tine20/Admin/Frontend/Json/UserTest.php
@@ -583,7 +583,8 @@ public function testExternalDomainInUserAccountCreate()
         $userArray = $user->toArray();
         $updatedUser = $this->_json->saveUser($userArray);
         self::assertEquals($userArray['accountEmailAddress'], $updatedUser['accountEmailAddress']);
-        self::assertFalse(isset($updatedUser['xprops']['emailUserIdImap']), print_r($updatedUser['xprops'], true));
+        self::assertFalse(isset($updatedUser['xprops']['emailUserIdImap']),
+            'user should no longer have email xprops:' . print_r($updatedUser['xprops'], true));
     }
 
     /**
diff --git a/tine20/Tinebase/EmailUser.php b/tine20/Tinebase/EmailUser.php
index f661cd20e6..eadb148745 100644
--- a/tine20/Tinebase/EmailUser.php
+++ b/tine20/Tinebase/EmailUser.php
@@ -494,7 +494,14 @@ public static function checkDomain(
         $_throwException = false,
         $_allowedDomains = null,
         $_includeAdditional = false
-    ) {
+    ): bool
+    {
+        if (!Tinebase_EmailUser::manages(Tinebase_Config::IMAP) ||
+            !Tinebase_Config::getInstance()->{Tinebase_Config::IMAP}->{Tinebase_Config::IMAP_USE_SYSTEM_ACCOUNT}
+        ) {
+            return true;
+        }
+
         $result = true;
         $allowedDomains = $_allowedDomains ?: self::getAllowedDomains(null, $_includeAdditional);
 
diff --git a/tine20/Tinebase/User/Sql.php b/tine20/Tinebase/User/Sql.php
index c9d21fb7ed..f1749134ef 100644
--- a/tine20/Tinebase/User/Sql.php
+++ b/tine20/Tinebase/User/Sql.php
@@ -1081,7 +1081,8 @@ public function updateUserInSqlBackend(Tinebase_Model_FullUser $_user, bool $_ge
         }
 
         if (Tinebase_EmailUser::manages(Tinebase_Config::IMAP)
-            && ! Tinebase_Config::getInstance()->get(Tinebase_Config::IMAP)->allowExternalEmail) {
+            && ! Tinebase_Config::getInstance()->get(Tinebase_Config::IMAP)->allowExternalEmail
+        ) {
             Tinebase_EmailUser::checkDomain($_user->accountEmailAddress,
                 true,
                 null,
@@ -1205,8 +1206,13 @@ public function addPluginUser($addedUser, $newUserProperties)
      */
     public function addUserInSqlBackend(Tinebase_Model_FullUser $_user)
     {
-        Tinebase_Config::getInstance()->get(Tinebase_Config::IMAP)->allowExternalEmail
-            || Tinebase_EmailUser::checkDomain($_user->accountEmailAddress, true, null, true);
+        if (Tinebase_EmailUser::manages(Tinebase_Config::IMAP)
+            && ! Tinebase_Config::getInstance()->get(Tinebase_Config::IMAP)->allowExternalEmail) {
+            Tinebase_EmailUser::checkDomain($_user->accountEmailAddress,
+                true,
+                null,
+                true);
+        }
 
         $_user->isValid(TRUE);