554 5.2.2 The Recipient's Mailbox Is Full Bounce Back Message
There's a script for that: 554 5.2.0 STOREDRV.Deliver.Exception:ObjectNotFoundException.MapiExceptionNotFound - NDR when users send mail in Exchange Online
Fix: can't delete OWA mailbox or calendar items
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This Message Wasn't Delivered To Anyone Because There Are Too Many Recipients Bounce Back Message
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Remote Server returned '554 5.2.0 - Microsoft Community