Is an A record for the domain itself mandatory?

[Joseph S D Yao]

On Mon, Apr 17, 2006 at 06:26:48PM -0400, JJ wrote:
> I guess this is something I haven't run across before. A company we deal 
> with deleted the A record for their domain ("example.com") but left 
> www.example.com in place. They also had two MX records in place, both 
> priority 20, that were different hosts than the www. record.
> 
> For whatever reason, our Exchange 5.5 mail server suddenly couldn't send 
> them email any more at about the same time, complaining about "host 
> unreachable". They're going to add the A record back tomorrow, but I was 
> wondering if such an A record was mandatory.
> 
> Thanks for any enlightenment you can share,
> 
> Ray 


The A record is absolutely not mandatory.  It used to be rare.

But if they don't have an A record for their domain that is the same as
their mail server, they must have an MX record for the domain that
points to the mail server, in order for mail to account at domain to work.
(An A record pointing to their Web server's IP address, as seems to be
more common these days, is absolutely irrelevant to e-mail unless there
is no MX record, in which case it prevents e-mail from working.)

It's not clear from what you are saying that the MX records were kept in
place (you use the past tense), but you also don't say they were
deleted.  If they were not deleted, they should have still worked.

Have you investigated whether both mail servers were in fact still
accessible from your MS Ex server?  Or whether other DNS changes of
which you had not been aware were also made, and the MS error messages
were poor as usual?

-- 
Joe Yao
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