Richard Frovarp wrote:
> I've heard Exchange and Notes/Domino in the past. I don't know if there
> is any truth to this or not.

I swear Domino did/does it so that they can claim faster queue clearing

In any case, be aware that caching of your involved MX and A records can
have drastic effects on where a server will attempt to deliver your
mail. If for any reason it has a cached A record for one of your lower
pref MXes, but none for your higher pref MXes, many will just attempt to
deliver to the lower pref MX rather than doing additional queries for
your higher pref MXes' A records. You see this happen more often when
the name server that is authoritative for the domain's MX record isn't
also authoritative for the A records listed in that MX record.