[Mimedefang] DNS and MX records

[Les Mikesell]

On Thu, 2006-05-11 at 00:50, Alan Premselaar wrote:
> > 
> > The place this is likely to be a problem is where you have
> > virtual web servers with names in lots of domains pointing
> > to the same box and you do want to accept mail for some
> > of those names.  Note that CNAMES take all the associated
> > data for the related A records, so if you have an MX for
> > the real A record, the CNAME'd names get it as well, and
> > if you don't, mailers will follow the CNAME to the related
> > A record.  
> 
> This last part doesn't make a lot of sense, considering it's not legal
> to use a CNAME entry as an argument for your MX record.

What I mean is that MX's get dragged along with CNAMEs if
one was associated with the target name whether you intend
that or not.

If you have an A and MX record for mainserver.mydomain.com
and CNAMEs for www.mydomain.com and www.otherdomain.com
that point to mainserver.mydomain.com you are publishing
MX records for those www sites since a CNAME gets all
data associated with its target name.

> of course, while an interesting topic none-the-less, none of this is
> directly relevant to MIMEDefang.  Just thought I'd be the one to say it. ;)

Agreed, but it can cause some surprises.

-- 
  Les Mikesell
   les at futuresource.com