New Shared Mailbox - getting error when sending emails

Hi Vasil,

I will create a testing shared mailbox to play with it... Email is sent to external recipient, yes. I do not believe it is mail flow or similar as that would affect all maliboxes.... however... as I mentioned... all mailboxes (even shared ones) are working fine... Except the shared ones that were creating recetly.

I've found a topic a guy described the same situation ... and looks like with MS tech support they got it fixed by removing permissions / re-adding permission / disabling automap (all these via PowerShell) and manually adding shared mailbox in Outlook....

So I will try that as well... However, still wondering why this is happening 😕