sub domain and mail exchange

[Barry Margolin]

In article <ShS14.1150$EH2.977 at client>, user <some at here.com> wrote:
>I;m creating a sub domiain here and was curious if its possible for the sub
>domain to have its own mail exchange? I've already created a sub.foo.com but

Sure.  You can have MX records on any name in DNS.

>when I create a new MX record in the ns for sub.foo.com and the machine is
>running sendmail ok. I can send and rec mail locally on the machine but when
>I mail to user at sub.foo.com it gets bounced back saying server not found. Do
>I need some sort of enry in the ns for foo.com as well?

If you've delegated a subdomain, the parent domain needs to have NS records
that tell everyone who the servers for the subdomain are.  E.g. in the
parent zone file you need:

sub  IN NS  subserver1.foo.com.
     IN NS  subserver2.foo.com.

If the subdomain servers have names in the subdomain, you also need A
record in that parent domain for them, e.g.

sub IN NS  server1.sub.foo.com.
    IN NS  server2.sub.foo.com.

server1.sub  IN A  1.2.3.4
server2.sub  IN A  1.2.3.5

This is necessary to avoid a deadlock (to look up server1.sub.foo.com's
address you need to ask server1.sub.foo.com).

-- 
Barry Margolin, barmar at bbnplanet.com
GTE Internetworking, Powered by BBN, Burlington, MA
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