RE: Changing servers
>> RedHat) to a debian server. I'm trying to figure out a
>> way that will cause least mail delays to our customers
>> whilst the dns records propagate (The IP's are going to
>> change for the mail server).
>a) lower the TTLs to almost zero
>b) wait $OLDTTL + $REFRESH seconds
>c) change the infos
>d) after checking, put the TTLs back to the normal value
>That way, the change is instantaneous.
You could also, if you are planning to drop the old server offline
immediately upon getting the new server running properly, set this up using
MX records. Set the new server's IP as a lower priority MX in the DNS files
and wait for it to propagate and then drop the old server offline. The SMTP
hosts on the other end *should* then automatically switch to the lower
priority MX record when they see that the normal MX host is unreachable and
start sending to it. You can then at your leisure set your DNS files to the
proper MX and let them propagate as normal with no interruption in service.