Re: Value of backup MX
John Goerzen wrote:
On 2004-11-09, Steve Drees <drees@rangebroadband.com> wrote:
John Goerzen <> wrote:
I'm looking at redoing my mail setup due primarily to spam filtering.
Over at http://www.tldp.org/HOWTO/Spam-Filtering-for-MX/multimx.html,
they are suggesting not to use redundant mail servers unless needed
for load balancing.
This is poor advice.
Could you elaborate a bit on why that is? The author is saying that
well-behaved (ie, non-spamming) MTAs would keep retrying for several
days anyway, so the only time a backup MX would really prevent mail loss
is due to an outage extending more than that time. What do you think?
yes, that's what they should do, but with all that spam and viruses and
oter nasty stuff, mail queues grow relatively big, and more and more
mail administrator set the queue lifetime to 1-2 days (iirc, in the old
days the queue life time was about 7 days) so if you're out formore than
a day or two... you loose mail
It seems to make a lot of sense to me, but it seems too that I must be
missing something.
I'd suggest having a backup MX but make sure you have all the filtering at
your backup that you have at your primary.
That's what I have now, but there are some things that can't be done so
well (or at the very least, only in a horribly kludgy manner).
For instance, if somebody sends a message to
nonexistantuser@complete.org, and it goes through the backup MX for
whatever reason, the backup MX accepts the message. When it gets to the
main server, it will reject it with a 550. The backup MX then has to
e-mail back to the sender a bounce message.
Now think what happens when viruses/spammers do this. My backup MX is
sending out a lot of bounce messages to potentially innocent victims for
this reason.
couldn't you just set a blackhole hole account ? (the problem with a
blackhole account is that if a user send mail to someuser@yourdomain.com
and it misses a letter or two of the email address, he won't find out
his email message was sent to /dev/null)
-- John
sin
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