OT: Seeking opinion about reverse-DNS lookups on SMTP HELO

[Paul Howarth]

HaJo Schatz wrote:
> To combat spam I have enabled reverse-DNS lookups of incoming SMTP 
> connections. If the FQDN does not match the HELO-Identity, I reject the 
> connection with a 550 Error.

I think this is asking for trouble and is arguably in violation of RFC 1123:

   The HELO receiver MAY verify that the HELO parameter really
   corresponds to the IP address of the sender. However, the
   receiver MUST NOT refuse to accept a message, even if the
   sender's HELO command fails verification.

> I have now found that this breaks communication even with reputable 
> (well, an international bank that is) peers. Dunno how much more mail I 
> may have lost through this... How are you out there handling that, are 
> you doing reverse-lookups?

I do reverse DNS lookups for information only.

AOL are only accepting mail from sites that *have* reverse DNS, but it doesn't 
matter much what the reverse DNS points to - see 
http://postmaster.aol.com/info/rdns.html

Paul.