Question : Exchange invite error

We have an Exchange user that when we send a calendar invite to him, we get back a 5.1.1 error indicating that another user doesn't exist.

Is it possible that he has his invites forwarded to an address that is now bad?

Answer : Exchange invite error

Never needed to install a hotfix to resolve this problem.

First check if the user was a delegate and is still listed. If they were, remove them.
If not, then remove all delegates from the account and add someone new who has never been a delegate. Then restart Outlook.
Remove that user from the list of delegates and add the required delegates back in again. That resets the delegate system by forcing Outlook to publish a fresh list to the server.

Simon.