Re: Sendmail DS "Smart" relay host using a name without an "A"record? (adding two groups)

#1 08-23-2008, 01:58 PM

On Sat, 23 Aug 2008 12:54:50 -0500, Doug Herr wrote:

> I was asked to update some sendmail configs, to change the name used in
> the DS "Smart" relay host setting.
>
> The current was mail.sample.com and the update was to mx.sample.com.
>
> mail.sample.com resolved into a set of "A" records, but mx.sample.com
> had only "MX" records.
>
> So, I was asked to set:
>
> DSmx.sample.com where mx.sample.com would *not* return any "A" or
> "CNAME" answers, but *would* return 5 "MX" records.
>
> Would this work?
>
> And if it would work, *should* it?
>
> My understanding here was that the point of a relay host was that you
> were to hand all mail to that host and let *it* do any and all MX
> queries. And, anyway, we are not talking about mail to
> joe@mx.sample.com, which should be the only reason to care about the
> above mentioned MX records (unless I am very mistaken about the point of
> MX records).

I should have considered checking for other relevant groups *before*
posting that question, sorry.

Note that this is really two questions.

1. Would sendmail query the MX records when figuring out where the relay
host is?

2. If sendmail did that, would that be "proper" use of DNS.

--
Doug Herr
doug*at*wombatz*dot*com

#2 08-24-2008, 11:31 AM

[ Unannounced Followup-To header pointing to a regional group ignored ]

In article <4c744$48b04fd9$c690d01b$24836@TSOFT.COM> Doug Herr
<doug@wombatz.invalid> writes:
>
>I should have considered checking for other relevant groups *before*
>posting that question, sorry.
>
>Note that this is really two questions.
>
>1. Would sendmail query the MX records when figuring out where the relay
>host is?

Yes.

>2. If sendmail did that, would that be "proper" use of DNS.

There's no RFC saying how sendmail should interpret its config file. It
may be "surprising" behaviour, but it can't be called "improper", and it
can be very useful in a large organization - you just put a generic name
in all the sendmail.cf's, and then you can use DNS to control where the
mail actually goes, including the power of using different- or equal-
prio MX records.

In any case the function can be trivially disabled by putting the name
inside [brackets] - then sendmail will only do A/AAAA lookup.

--Per Hedeland
per@hedeland.org

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