running master, slave on the same computer

[Jesper Dybdal]

phn at icke-reklam.ipsec.nu wrote:

>If the MX for a domain is known but the mailserver ( target of MX) is
>unreachable mail will be stored and transmitted later. If dns don't work at 
>all the mail will bounce at the sending server.

That is the opposite of my experience.

It is my impression that all decent mail server software is quite
capable of distinguishing between "Domain does not exist" and "Because
of a DNS error, we don't know whether the domain exists" - and keeping
the mail queued in the latter case.

I would consider it a bad bug for an MTA to bounce a message
immediately just because of a problem with DNS service.  Otherwise,
mail would also bounce if the MTA itself was temporarily cut off from
the internet and therefore from all external DNS service - and that is
not what happens in practice.
-- 
Jesper Dybdal, Denmark.
http://www.dybdal.dk (in Danish).