On Tue, 5 Jul 2005, Jim Popovitch wrote:
Generally there's little reason to run a secondary MX. Email will queue if the sole MX is offline or unreachable. Email will queue at senders' mail servers.
The problem with the above is that your (or your users') email delivery is then dependent upon the configuration and timeouts of someone else's system (my system drops undeliverables after 1 hour).
True -- however, too many people have so grossly misconfigured secondary MXs in "traditional" operation mode, in the face of today's blowback bounce spam world. Traditional secondary MXs are going the way of open relays, *quick*. The default recommendation I give anyone these days is to use no secondaries, and let the sender's mail server queue it up, as that's the fastest implementation path. As a second stage, and only if the expertise and time is available, then a backup MX with some sort of recipient validation at SMTP time can be implemented. -- -- Todd Vierling <tv@duh.org> <tv@pobox.com> <todd@vierling.name>