[ALUG] Re: MX/Zone/DNS question

[Wayne Stallwood]

On Fri, 2007-01-26 at 13:52 +0000, Mark Ridley wrote:
> Since no MX record exists (unless you have wildcarded *.isbd.net) for
> home.isbd.net then mail will be routed to the A record for that host.
> You
> should not use CNAMEs with anything mail like.
> 
> >From the sendmail docs:
> 
> "If no MX records are available for a given host, sendmail will try to
> send to that host directly. Once sendmail determines which host to
> attempt
> to send the message to: an intermediate host as indicated by an MX
> record,
> or a direct connection to the target host, it uses gethostbyname() to
> determine the IP-address of the target machine in order to make a
> connection."
> 

I am not sure that would work if the senders MTA is something like
Exchange

"To determine mail hosts, the sending Exchange server checks for an MX
record. Next, the sending server resolves the MX record to an IP address
by checking for an address (A) record.

If MX records for remote domains are missing, this may cause messages
destined for the remote domains to back up in the Exchange server Remote
Delivery queues in addition to other routing or service delays."