Oh yeah, cable modem!
The always on connection that ALMOST never gets reset and picks up a new IP address!
Yes that's right.
Suddenly it was 'oh no that couldn't be it, could it?"
Went to http://ipchicken.com
to check my public IP address!
And guess what it had changed.
That's the second time in about nine months.
Oh well, at least the incoming e-mail is working now.