[Mimedefang] Slightly OT: Advice on updating MX record (was SMTP error return after DATA?)

[Michael Sofka]

On Friday 09 May 2003 15:19, Michael Sims wrote:
> So, I was thinking about getting the new server up and running it in
> parallel at first, and adding it as a secondary MX record with a lower
> preference.  I could then wait for that change to propagate out, then
> switch over to the new setup with the new server as the sole MX record.
>  That way sites that are slow to update DNS should theoretically fall back
> to the secondary MX when the first one rejects their connection.

Yes, this is the best way to switch MX.  You will have to be sure to
avoid local MX loops.  You will also find a number of connecting relays
that continue to connect to the wrong machine weeks later---even if
you push out a short TTL time.  You will have to contact the admin
of those machines (or wait until they call you).

One warning.  If the actual IP of the mail machine changes, Window
and MacOS machines will not use the new IP until rebooted.

What we did when mail switched (new MX and IP) in February was us
MIMEDefang to email a notice to check configuration and reboot if
necessary when *.rpi.edu machines where connecting to the old server.

Finally, regarding spam.  The spammers will continue to connect to
the old machine long after it is no longer accepting email.  We are
blocking these at the firewall, and still seeing several hundred
a day (with occasional busts of more activity).

Mike

-- 
Michael D. Sofka              sofkam at rpi.edu
C&CT Sr. Systems Programmer    Email, TeX, epistemology.
Rensselaer Polytechnic Institute, Troy, NY.  http://www.rpi.edu/~sofkam/