Traditional Mail Server Configuration has always taught that it's a
good idea to have a Backup MX Server configured for your domain so
that if your SMTP Server or subnet were to go down, mail for your
domain could still be received. So for as long as I can remember,
we've had a backup MX hosted by our ISP. However, more recently,
spammer techniques has caused me to rethink the usefulness of a
Backup MX Server which accepts all mail for delivery, without spam
filters or rcpt checking. We've used Spamhaus RBL somewhat
effectively to block at the SMTP level, but I believe many spammers
connect directly to our ISP's backup MX to send mail, effectively
bypassing our RBL checks. It also means we can't outright reject
flagrant virus messages at the SMTP level (at least not ones from our
backup MX) since the backup MX has already accepted the message from
the server of origin thus causing a bounce and an innocent user
receiving a message that they've sent out viruses.
So here's my question, would it be risky to drop the backup MX
completely? We're on a T1 that has been extremely reliable the past
few years. Should we have an outage, we'd have 4 hours I believe
until most mailservers would start generating delayed delivery
messages back to remote senders and 4 days before most mail servers
would give up on delivering a message (in which case we'd have time
to update the DNS most likely). In an ideal situation, we'd have
redundant internet connections and a MX on both networks, both with
the same rcpt verification and spam/virus filtering configuration but
we just can't afford that now. I could setup a MX server on our
subnet in case the main mail server goes down but that wouldn't help
against ISP level outages. Our domain hosts about 1500 accounts,
What do you do?
Wow that got long...
Jay
--
Jay Lee
Network / Systems Administrator
Information Technology Dept.
Philadelphia Biblical University
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