On Tue, 6 Aug 2002 22:12:01 -0400
"Telent" <telentmordac.info> wrote:

> > Right now, the MX record for the-bob.org is cricket.the-bob.org, with
> > a value of 10. I just deleted it to see what happens when there's no
> > MX record, but I thought you needed to have one for a domain that was
> > going to receive mail.
>
> This is a common misconception.
>
> You DO NOT need a MX if the machine that the-bob.org points to also
> handles mail.

You should use them anyway. There are some really flaky mailers out
there and some of them may not deliver e-mail without proper MX records.

From DNS and Bind, Third Edition, pages 94-95:

  What if a host doesn't have any MX records? Will a mailer
  simply not deliver mail to the host? Actually, you can
  compile recent versions of sendmail to do just that. Most
  vendores, however, have compiled their sendmails to be more
  forgiving: if no MX records exist, they'll at least attempt
  delivery to the host's address. senmail version 8, compiled
  "out of the box", will try the address of a mail destination
  without MX records. ...

  Even though nearly all mailers will deliver mail to a host
  with just an address, and no MX records, it's still a good
  idea to have at least one MX record for each host. sendmail
  will request MX records for a host each time it needs to
  deliver mail. If the host doesn't have any MX records, a
  name server -- usually one of your authoritative name
  servers -- still ends up answering that query. If you simply
  add an MX record for the host pointing to itself, sendmail
  will have its first query answered, and the mailer's local
  name server will cache the MX record for future use.

Besides, it takes very little effort to set up an MX record, so
there is little excuse not to go ahead and set it up.

> MX records are only used if you wish to have one machine handle, say,
> web, for the-bob.org, but not mail.

Most people use them anyway, just to be safe.

Also, you might want to designate a second machine to catch the e-mail
in case the first is down.

Eric Johnson

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