Cannot load valid user, but user exists


Running v 3.0.2 on FreeBSD 4.8.

I have a client that sends email via an Exchange server (only "different"
thing I can find about this client vs others).

It creates the account and opens the ticket. He gets confirmation of the

I update the ticket and he gets the update.

If he then tries to update the ticket via email from that same account, it
kicks back the “cannot load valid user” message.

This is the only client I’ve had this problem with. In fact, if he uses his
yahoo account, it works fine.

Any ideas?