Subject: Re: sendmail inappropriately tries to externally relay local mail
To: Christian Hattemer <email@example.com>
From: Chuck Swiger <firstname.lastname@example.org>
Date: 08/31/2005 18:42:03
Christian Hattemer wrote:
> I have a 3.0_BETA box, installed from source dated June, 15.
> Everything was fine, until lately the name "localhost.myisp.de" appeared in
> DNS. Since that sendmail tries to relay local mail (e.g. reports from
> /etc/daily) via "localhost.myisp.de". It seems the name is built from my
> hostname "mybox.myisp.de" by taking "localhost" and appending the hostname
> minus the first part.
Doesn't "dig localhost." and "dig localhost" and "dig localhost.myisp.de" all
> I haven't changed anything myself when the problem occured. Generally the
> related parts should be mostly unchanged from installation.
> It seems that sendmail is misconfigured and always looks for such strange
> localhosts. But unless there is one everything works ok.
Perhaps your sendmail is misconfigured. You should set the canonical hostname
to be a fully-qualified value, and you should ensure that sendmail sees this.
Consider the output of:
echo "3,0 user@localhost" | sendmail -d0.1 -bt
> On a look at Google I saw a lot of descriptions of the symptoms but no
> working cure. It also seems to be a game amongst DNS admins to put such a
> localhost in their zones since I saw a lot of these.
It is normal and encouraged to map localhost.example.com to 127.0.0.1 via an A
record. This helps misconfigured clients which can't resolve localhost without
doing a DNS query get a reasonable answer immediately, rather than querying
each domain (and subdomain, perhaps, for especially broken resolvers) in their