[office365] Message Attachment Size Limit Error

There has been a significant reduction in the number of failures for Office 365 requests with attachments larger than 3 MB. We will continue to monitor.

Office 365 servers may sometimes fail to accept attachments larger than 3 MB. As a temporary alternative, we suggest using another method of sharing files with recipients, such as OneDrive. We have communicated the issue to Microsoft and are investigating additional mitigations.

We received reports from a small number of customers that some drafts error when sending, with the message:
"Unexpected problem sending attachment larger than 3MB to Office 365."