Incoming emails are stuck in SharePoint 2010 server Drop folder

First symptoms

  • Emails sent to SharePoint library address don’t reach destination.
  • No error message returns to sender

What to check to identify the issue

  • Incoming email “Drop” folder on SharePoint WFE – all missing emails should be there, awaiting to be picked up by SharePoint
  • ULS logs has the following error with “E-mail” category:

    The Incoming E-Mail service has completed a batch. The elapsed time was 00:00:00.0156241. The service processed 4 message(s) in total. Errors occurred processing 4 message(s): Message ID: Message ID: Message ID: Message ID:

Resolution

It was hard to find it because of misleading info, so I post it here.

Update: the issue was fixed in May 2015 CU. Keep reading if you cannot install this CU, need temporary workaround or you are just naturally curious.

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