Outlook For Mac Attachments Warning


Step 1: Click the File Options. Step 2: In the Outlook Options dialog box, click the Mail in the left bar. Outlook for Mac is a disk space hog but the macOS has a way to recover some of that. Mac computers can have relatively small hard drives like 128GB or 265GB which Outlook 2016 for Mac can gobble up. Unfortunately, Outlook for Mac, even the latest Outlook 2016 doesn’t have some of the space saving options available to Office for Windows.


Original KB number: 3146087



You use Microsoft Outlook 2016 for Mac or Outlook for Mac 2011 to connect to a mailbox on a Microsoft Exchange server. When you send an email message that contains a large attachment, you receive the following error messages in Outlook for Mac.

Or, you receive a non-delivery report (NDR) in your Inbox like this one:

Outlook 2013 attachment security warning

The message contains diagnostic information for administrators, such as the following:

Remove Server returned '500 5.2.11 RESOLVER.RST.SendSizeLimit.Sender; message too large for this sender'


Outlook 2013 Attachment Security Warning


This issue occurs when you send an email message that's larger than the Exchange Web Services (EWS) message size limit that's configured on the Exchange server.


Visual studio mac not starting. You can increase the message size limit on the Exchange server to allow for larger email messages to be sent from Outlook for Mac clients and other EWS clients. For more information, see the following TechNet articles as appropriate for your version of Exchange Server.

Exchange Server 2016 and 2013: Configure client-specific message size limits

Exchange Server 2010: Set message size limits for Exchange Web Services

More information

For more information about this issue, see the following article in the Microsoft Knowledge Base:

Outlook Attachment Security Warning

3107326 You can't send large attachments by using the EWS client