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I have come across a very unique problem that I have yet to find a solution for as even google failed me.

When User1 tries to send a mail as the shared Mailbox SharedMailbox@ourdomain.com the mail is being placed in the outbox and does not show up in any logs. However if User2 sends a mail as the shared Mailbox, User1‘s mail is also being send out of the outbox with no problem. At this point User1‘s mail also shows up in the logs.

What I have tried:

  • restart Exchange
  • create new mail for User1
  • try different outlook clients on multiple PCs
  • move User1‘s mailbox to a different database
  • assign User1‘s rights freshly (all right including send as)
  • copy the AD user and try it with the copy, which has the same problem as User1)

Seeing as User1Copy has the same problem as User1 I snooped through the attributes in AD and changed every attribute that was different from User2, but still it does not work.

Two days ago it randomly sent out the mail from the outbox without someone else sending a new mail (I checked the logs).

Does anyone have an idea what else I can try (besides making a new AD user for User1) or if I can access the outbox via the Exchange Server Shell?

Kyoshi
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  • 1. Did the user2 send emails as the shared mailbox successfully if nobody used this mailbox at the same time? Or the issue only happened on user1? 2. What happens if user1 sends emails as the shared mailbox via OWA? – Ivan_Wang Sep 09 '21 at 06:11
  • (Apologies for the very late reply) 1. No. Even if nobody else is using it, the mails keep getting stuck in the outbox. 2. The same problem occurs Using PowerShell on the exchange server I could make out that even if the Out Box is visibly empty, there is still 1 Item listed under ItemsInFolder. However I have yet to find a manage to pin down that Item. I am thinking that if I delete it, it might work. – Kyoshi Sep 21 '21 at 13:11
  • Try to restart MSExchange Transport/Frontend Transport service on your Exchange server and see if there is any difference. – Ivan_Wang Oct 05 '21 at 05:19

2 Answers2

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Check if there is a registry key DelegateSentItemsStyle added on user's client: Email remains in the Outbox when you use the DelegateSentItemsStyle registry value

Ivan_Wang
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  • I've checked that but there is no such registry key set. I also tested it on different machines alltogether. – Kyoshi Sep 21 '21 at 13:10
  • Because the issue also happened in OWA, the issue seems to be related with the ACL Perhaps you could add the send-as permission by running the following command and see if there is any difference: **Add-AdPermission -Identity -User -AccessRights ExtendedRight -ExtendedRights "Send As"** – Ivan_Wang Sep 24 '21 at 10:25
  • We've tried that as well, but I've just now run it again in case I messed up the first time. The problem still holds. – Kyoshi Sep 27 '21 at 13:46
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Unfortunately we've not manged to find out what caused the problem. I couldn't spend more resources on it so we opted for canning the Mailbox and creating a new one.

Sorry that there is no happy end to this.

Kyoshi
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