Silly Redhat
Well, my DTA is working after about two days of being "broken". Turned out it was on their end after all.
While trying to figure out how to migrate "client B" from below from sneezy to bashful (dopey isn't online yet) I remembered that the new Redhat Enterprise Linux (and I think Fedora too) doesn't support user names with dots in them, so for example sruli.the.grate@alsonetworks.com wouldn't be allowed. Sneezy is my last Redhat 7.3 box, so all clients with those kinds of addresses are on that box.
Eventually I found a patched RPM here...
http://ftp.pslib.cz/pub/users/Milan.Kerslager/RHEL-3/RPMS/
...that solves this. Who knows what it means for future upgrades?
Why would Redhat disable this? So many people use the format first_name.last_name@mydomain.com as an email address!
Gonna move the client as soon as I have tested. In the mean time there was a 15 minute period of down time on sneezy AGAIN today. Phooey. Tzirel got to do th...