Emails stuck in outbox




We have a user that frequently sends email from a shared mailbox. Some of these emails never leave the outbox, some are actually being sent, and some are not. This happens on a daily basis. I've searched for similar problems online and have tried a few suggestions, like:

- cleaning up the users mailbox (went from 22 to 7 GB)

- gave user a new Outlook profile

- disabled downloading of shared folders

- made the shared mailbox default mailbox


This morning she has two emails stuck in her outbox, one of them (an internal email) has been received.


Any help would be appreciated.




5 Replies
I have the same issue.

Has been a problem for 18 months or so, on and off.

A real PITA because sometimes I don't realise a business email hasn't been sent for several hours - makes my company look bad.

Tried all the above plus disabling cached exchange mode.

Most emails send OK, a few get stuck. With cached Exchange mode the Outbox would show [2] emails but when you click the folder there was nothing in it.
A little more info about this. Automatic archiving is enabled for this mailbox but I'm not sure that it's working. Archiving is set to 90 days but there are items in deleted and sent items that are more than a year old. Items in inbox go back to August of last year.
Total mailbox size is now 30 GB.


Did you encounter the same when operate in OWA?

User will spend the entire day tomorrow working in OWA to see if she experiences the same problem there. Will let you know how it goes :)

@aaanne our scenario is that the "Shared" mailbox was a regular Office365 mailbox that multiple users added to desktop Outlook as an additional account. It worked fine for many years like this.


Yesterday I ran the SARA tool (Microsoft Support and Recovery Assistant) and it came back saying there was a licensing issue with the account and that we should use a shared account instead.


The regular O365 mailbox actually had a valid license so the license was fine.


However what I did was to convert the regular O365 mailbox to a shared mailbox in the O365 admin control panel.


Will monitor the situation and see whether we continue to get any sending issues with the new configuration.