I have an internal Exchange 2010 server, single domain, standard setup, AD environment, nothing really special. Users are all on Outlook 2010.
I have one user that just recently started getting reports that when people reply to his emails, they bounce back. Checking into it, I was able to replicate (though no idea how/why this particular email manifested the issue, while others did not), and it appears that in the email header, his Reply-To shows his correct username, but instead of ..domain.com, it is ..domain.cim.
This happens both with internal emails as well as external.
On Exchange, I verified his SMTP address is showing as .com.
In outlook, I tried reselecting his account as the "reply to" address.
What could be causing this?