Granting delegate access to a mailbox stores the permission on the mailbox to which the permission is granted. But what happens when a user is deleted? The simple answer is nothing - deleting a user (or other AD object) does not delete references to that object in other places. What this means is that...

We recently had a case where there were invalid delegates on a mailbox and these were causing further issues (which aren't important with regards to this blog!). Invalid delegates can come about when mailboxes and users are deleted from an organisation. The reason for this is that delegate permissions...