Wrong SMTP server

I route email thru our IT department's Exchange server. On the General tab
of my SMTP server, the "Use mail router" shows the correct hostname. A
5250 ping of that hostname resolves to the correct IP address. I bounced
my SMTP to ensure the displayed values are live.

IT tells me that my emails are going to an old obsolete mail server. My
TCP connections show two connections with the Remote Address of the wrong
mail server with Remote Port of 25. I don't have any connections using the
correct mail server IP. Emails I send show the wrong mail server in the
headers.

Any idea what to check?