Multiple CNAMEs - howto?
Andy Shellam (Mailing Lists)
andy.shellam-lists at mailnetwork.co.uk
Mon Oct 30 23:52:04 UTC 2006
>> Not all depending on the definiton of "mail clients".
>> For Postfix and Sendmail I am sure that the use MX before A on outbound
>> But if we are talking over products like OE I can not say that.
Yes, I was talking more about "dumb mail clients" (ie. not MTA servers
acting as clients). MTA servers yes, would use the MX records to first
try and deliver a mail.
OE, Thunderbird, etc. expect a server name as their outgoing server (eg.
exchange.mailnetwork.co.uk). If they tried to do an MX lookup on that,
they'd get nothing, as only the root domain (mailnetwork.co.uk) has MX
records, and I don't believe (might be wrong) the clients are clever
enough to work out the primary domain.
I'll stick to what I had, it's doubtful the server IPs will change often
anyway (maybe once a year if at all) so it was only a minor problem -
more of a "can this be done?" rather than "I need this!" sort of question
>> Incoming messages is not a problem - they *should* come to uk1
>> primarily, and only to uk2 or 3 if the previous are unavailable.
>> For that I have the setup:
>> $ORIGIN mailnetwork.co.uk.
>> IN MX 10 uk1
>> IN MX 20 uk2
>> IN MX 30 uk3
>> It's for outgoing messages so users can either connect to
>> exchange.mailnetwork.co.uk (which will in effect be a round-robin for
>> all 3 servers), or directly to uk1, 2 or 3.
>> I believe mail clients use the A records for SMTP?
> Not all depending on the definiton of "mail clients".
> For Postfix and Sendmail I am sure that the use MX before A on outbound
> But if we are talking over products like OE I can not say that.
> I found this (old) discusion http://www.nber.org/redundant.html .
> But I only can say check it.
> So check your query logfile.
> Even if you would have mutiple A records you should alway's see MX lookup
> request for that RR.
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