Weblog entry #9 for dkg
Given that MTAs are increasingly complicated these days (with various spam filtering techniques), what are some good arguments for (or against) having multiple MX records for a relatively small domain (<1000 users)? Here's a couple notes of my own (which i'm not wedded to: please tell me if you disagree!):
- more control over mail delivery: if your primary MTA is down or unreachable, you still have a machine you control who will accept mail deliveries on your behalf, rather than trusting the remote mailer to retry properly.
- it's "the standard" way to do things.
- redundancy is good.
- synchronizing settings between primary and secondary MTAs is complicated and potentially error-prone. If settings are not synchronized, the secondary MX could end up accepting messages for delivery that the primary would not have accepted.
- simplicity is good.
- queues on the secondary MX provide yet another place for mail to be lost or mangled in an already-complicated protocol
- i've heard many reports of spammers preferring the secondary mail exchangers over the primaries, though i'm not clear why that is.
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