Eliminating the "www" Portion of a URL

Barry Margolin barmar at bbnplanet.com
Tue Mar 14 17:11:10 UTC 2000

In article <200003141653.KAA20332 at achilles.ctd.anl.gov>,
Barry Finkel  <b19141 at achilles.ctd.anl.gov> wrote:
>Cricket replied:
>>I imagine there are still some misguided mailers out there that use
>>the address record for a domain name instead of the MX records
>>to determine where to deliver the mail.
>Last week I worked on a mail problem with a Macintosh-based mailer.  
>When it tried to send mail to 
>     aaa.bbb.ccc.com
>and it did not find an MX record for the full name, it did NOT look for
>an "A" record; it then looked for an MX record for the sub-domain
>     bbb.ccc.com

That's the parent domain, not a sub-domain.

>and in our case, that MX record pointed to a different mail host than
>the "aaa" node, where the recipient's mailbox resides.  Once I added
>an MX record for aaa that pointed to itself, mail from this Mac mailer
>was deliverable.

That mailer is totally broken.  Nothing in the Internet standards suggests
this behavior, and they specifically say that the A record for
aaa.bbb.ccc.com should be used if there's no MX record.  The MX record is
used as a way of redirecting mail away from the host; the "normal" action
is to send the mail to the host specified in the email address.

I could understand this behavior as a fallback if aaa doesn't have an MX
record or A record.  However, if that's the behavior that the destination
site really wanted, they could easily have installed a wildcard MX record
(basically, the sending mailer would be pretending that the bbb.ccc.com MX
record is also a wildcard MX record).

Barry Margolin, barmar at bbnplanet.com
GTE Internetworking, Powered by BBN, Burlington, MA
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.

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