Do I need MX record at all?

[David Botham]

bind-users-bounce at isc.org wrote on 04/19/2005 06:48:12 PM:
> 
> --- unix at edify.com wrote:
> >    I would like to know if MX record is needed at all reason is I am
> > using Sendmail (8.12.11)on the same DNS server that uses mailertable 
which
> > has entries to tell where it needs to pass on email. I have Checkpoint 
FW
> > rules to tell how the email should be routed, so do I really need MX 
record
> > for the outside world to tell where email should be delivered to. 
> 
> An MX record is not mandatory, but it is WISE.

Not using an MX RR is only possible when there is an A RR for the 
potential owner of the MX RR.  That is to say, if you think you need the 
following MX RR (with the associated A RR for the MX RR's RDATA):

foo.com.  MX  10  mail.foo.com.
mail.foo.com  A  192.168.1.5

Then you could omit the MX RR and its associated A RR by using the 
following A RR:


foo.com.  A  192.168.1.5



The rest of the previous poster's comments regarding backup mail servers 
still applies.  You *will need* MX RR's if you have more than one mail 
server.  Multiple A RR's will not do the trick for a number of reasons. 
Remember, the "preference" field should be thought of as a cost, i.e. the 
lower the preference, the more preferred the mail exchanger...


hth,


Dave...


> 
> Some mail filters look for an MX record, no MX 
> no email from that domain.
> 
> Here?s how an MX record would help you, your net hole is 
> down for some reason, car bombing, backhoe, anthrax, 
> jet liner, or whatever. 
> 
> You have back up mail servers on different works, across the country.
> 
> You are down for a few days, but do not lose any mail (in).
> 
> You don?t have to plan for a falure, but one is planning on you.
> 
> -charles
> 
>