diff --git a/NEWS b/NEWS
index 00f27bc03..d38499215 100644
--- a/NEWS
+++ b/NEWS
@@ -22,6 +22,7 @@ Bug fixes
  - [web] respect SOGoLanguage and SOGoSupportedLanguages (#4169)
  - [web] fixed adding list members with multiple email addresses
  - [web] fixed responsive condition of login page (960px to 1023px)
+ - [web] don't throw errors when accessing nonexistent special mailboxes (#4177)
  - [core] newly subscribed calendars are excluded from freebusy (#3354)
  - [core] don't update subscriptions when owner is not the active user (#3988)
  - [core] strip cr during LDIF import process (#4172)
diff --git a/UI/MailerUI/UIxMailFolderActions.m b/UI/MailerUI/UIxMailFolderActions.m
index 82fbdf2bf..17c4b140d 100644
--- a/UI/MailerUI/UIxMailFolderActions.m
+++ b/UI/MailerUI/UIxMailFolderActions.m
@@ -714,9 +714,17 @@
   error = [co expunge];
   if (error)
     {
-      data = [NSDictionary dictionaryWithObject: [self labelForKey: @"Unable to expunge folder." inContext: context]
-                                         forKey: @"message"];
-      response = [self responseWithStatus: 500 andJSONRepresentation: data];
+      if ([co isSpecialFolder])
+        {
+          // Special folder probably doesn't exist; ignore error.
+          response = [self responseWithStatus: 204];
+        }
+      else
+        {
+          data = [NSDictionary dictionaryWithObject: [self labelForKey: @"Unable to expunge folder." inContext: context]
+                                             forKey: @"message"];
+          response = [self responseWithStatus: 500 andJSONRepresentation: data];
+        }
     }
   else
     {
@@ -730,7 +738,7 @@
           response = [self responseWithStatus: 200 andJSONRepresentation: data];
         }
       else
-        response = [self responseWithStatus: 200];
+        response = [self responseWithStatus: 204];
     }
 
   return response;
diff --git a/UI/MailerUI/UIxMailListActions.m b/UI/MailerUI/UIxMailListActions.m
index 8436b3a68..293473291 100644
--- a/UI/MailerUI/UIxMailListActions.m
+++ b/UI/MailerUI/UIxMailListActions.m
@@ -767,6 +767,10 @@
 
   if (data != nil)
     response = [self responseWithStatus: 200 andJSONRepresentation: data];
+  else if ([folder isSpecialFolder])
+    {
+      response = [self responseWithStatus: 204];
+    }
   else
     {
       data = [NSDictionary dictionaryWithObjectsAndKeys: