[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

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



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.


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]