Reverse lookups in Sendmail

[smikes19]

Here is my situation. It is not in production yet, as I'm trying to figure out if this will cause problems.

I've got one dns server that is the primary DNS for 3 different domain names. All mail from these domains get relayed to one mail server.

My question is, how should the reverse lookups on the dns server be setup? It seems logical that you can only have one reverse lookup table, and my concern is that if I send mail out as xxx.com, a reverse lookup might show the host as yyy.com or zzz.com.

Are sendmail servers out there in the world going to care about this?

 

[fluid11]

A reverse lookup maps a hostname (xyz.com) to an IP address, not another host. A reverse lookup on any of the 3 domains will all point to the same IP.

ChrisP ------------------------------------------------------------------------------
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[smikes19]

A reverse lookup resolves an ip address to the appropriate domain name.

Thanks for the reply ChrisP, but I think theres a misunderstanding so let me elaborate.

named.conf -

db.xxx.com:
host1 in a 192.0.0.1
host2 in a 192.0.0.2

db.yyy.com:
host1 in a 192.0.0.1
host2 in a 192.0.0.2

db.zzz.com:
host1 in a 192.0.0.1
host2 in a 192.0.0.2

db.0.0.192-in.addr.arpa:
1 PTR host1.xxx.com ????? or yyy.com???
2 PTR host2.zzz.com ???? or xxx.com????

end of named.conf

All 3 domains basically point to the same hosts.

So if 192.0.0.1 sends mail out as xxx.com, and the remote
sendmail box does a reverse lookup, it will find that IP resolves to host1.xxx.com or yyy or zzz. Should I be concerned with this? Will mail ever be rejected by remote sendmail servers? Can I only send mail out as specified by the reverse lookup mapping?

 

[fluid11]

Oh, right, what was I thinking

I wouldn't be concerned with it. Most mail servers don't do reverse lookups on every piece of mail they receive anyway. This would significantly decrease the performance of the server, especially a high volume server.


ChrisP

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