On Fri, Feb 13, 2015 at 9:57 AM, Ken Smith <kens@xxxxxxxxxxx> wrote:
> Hi All,
>
> I'm just wanting to check that my understanding of the settings is correct
> as my web searches are finding a lot of dated information.
>
> If I want a Centos 6 sendmail system act as the secondary MX for domain
> bbbbb.co.uk do I just add a
>
> Connect:bbbbb.co.uk RELAY
>
> statement into /etc/mail/access and restart sendmail
>
> Obviously I have the DNS MX records for the domain are already established.
>
> I've been getting "/config error/: /mail loops back to me/ " errors.
>
> I think I may be stumbling into a variant of cname problem where the
> hostname as far as the sendmail machine is concerned is aaaaa.com but the
> DNS setting for the secondary MX is smtp1.bbbbb.co.uk.
>
> They both resolve to the same IP but when sendmail looks up the MX records
> for bbbbb.co.uk it will find smtp.bbbbb.co.uk and smtp1.bbbbb.co.uk listed
> and it may relay the mail off to smtp1.bbbbb.co.uk without recognising that
> aaaaa.com = smtp1.bbbbb.co.uk. Am I on the right track here, as I then just
> need to change the secondary MX setting in DNS to aaaaa.com?
I'd recommend not having a secondary MX at all unless it is equipped
to reject invalid users and spam in all the same ways as your primary.
Otherwise it accept junk that your primary rejects and then you are
obligated to send a bounce message which is always a bad thing - you
want the authoritative receiver to reject at the smtp level instead of
accepting at all. There's a whole category of spam where the real
target is the apparent sender where a bounce will go. Also anything
sending valid mail should be prepared to queue and retry on temporary
failures just as well as your own secondary would.
--
Les Mikesell
lesmikesell@xxxxxxxxx
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