A few weeks ago, my ISP (Cox) changed what outgoing server I must use.  Old one was "smarthost.coxmail.com"  New one is "smtp.east.cox.net".

This works fine when I put in the new server; however, when I come back the next day, the settings have somehow switched back to the old server.  As a result, I can't send email until I change it to the new one.

Cox knows nothing about this, and tells me that I must have a virus.  I scanned with several antivirus and anti-malware programs, and it seems clean.  Note that "smarthost.coxmail.com" used to be the correct server for me, but they have changed it.

I set up a new account using the new server, and it stays correct.  However, I have 2 old accounts that keep switching back sometime during the night.

Any ideas?