MX records in reverse zones

[Cricket Liu]

> Does it make sense to have MX records in a reverse zone? If so, how so;
> if not, why not?

No, it doesn't, unless you expect people to try to send mail to,
for example user at 1.0.168.192.in-addr.arpa.

> I haven't done very exhaustive checks, but so far none of the other
> networks I've looked at (including MIT) have had MX records for their
> reverse lookups, and I can't see much use for it myself. Perhaps to
> allow MX-ed emailing to IP addresses?

No, because if you send mail to user at 192.168.0.1, the mailer won't
look up MX records in the corresponding reverse-mapping zone.

> The reason I ask is that I'm rewriting an ancient program that builds
> our zone files from a database. The current program stuffs the same
> nameservers and the same MX records blindly into every zone file.
> 
> Try "dig 132.129.in-addr.arpa mx" to see the effect. 

Looks like a weird artifact of some improper coding to me.

cricket

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