Use of MX Records

[Kevin Darcy]

Barry Margolin wrote:

> In article <946tgg$75u at pub3.rc.vix.com>,
> Smith, William E., Jr. <Bill.Smith at jhuapl.edu> wrote:
> >
> >According to O'Reilly's 3rd Edition DNS & BIND book each host should hae at
> >least one MX record.  Furthermore, it suggests adding an MX record pointing
> >to itself.  Should this be the case for all hosts, even say a Windows box
> >which has no mail server, etc running on it.  Right now, we have 3 MX's
> >generated for each host.  Itself, and our two main mail servers.  Some here
> >have expressed concern over the use of MX records for workstations that
> >really don't need them since they aren't having mail delivered directly to
> >their box.  Just wondering if it's really necessary/optimal to add an MX for
> >each host, even though they may not really need it.  Insight would be
> >appreciated.
>
> MX records are only necessary for hostnames that are expected to appear in
> email addresses.  If you never send mail to user at something, no one will
> ever try to look up the MX record of "something", so there's no need to
> have one.
>
> And if a machine doesn't run a mail server, you should never have an MX
> record that points to it.

Actually, _DNS_and_BIND_ is a little confusing on this point. It literally says
"..., it's still a good idea to have at least one MX record for each host",
although admittedly it's in the context of delivering mail to hosts by either MX
record, or, failing that, A record.

Perhaps 4th Edition could clarify this a bit?


- Kevin