Question : RFC Mailing via dynamic IP

Hi there!

I have a question about mailing. Our server is located in another from my country. When it it tries to send email to @mail.ru it meet a problem:

The following recipient(s) cannot be reached:

      [email protected] on 21.10.2009 12:13
            There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
           

Is there some RFC which describe sending via dynamic IPs. As I understood mail servers MUST NOT refuse mailing from such kind of servers.

Answer : RFC Mailing via dynamic IP

Enforcement of RFC 1912 is generally enough to block clients on dynamic IP addresses. That one has little to with SMTP specifically, it suggests that all Internet hosts should have both Forward and Reverse Lookup in place. See 2.1 in RFC 1912 (http://www.ietf.org/rfc/rfc1912.txt).

SMTP is one of the few (if not the only) place you will find this strictly enforced. The original SMTP specification gave us absolutely nothing to secure the system, which leads to additions such as SPF, discussed in RFC 4408 (http://www.ietf.org/rfc/rfc4408.txt).

It's worth looking at RFC 2821 again as well, the 550 response code gets a new reason between RFC 821 and RFC 2821: The addition of refusal for Site Policy reasons, it is not further qualified within the RFC but would be exactly the right error code to return in this instance.

At the end of the day, you can hardy blame them for dropping dynamic IP addresses these days. The amount of spam flowing from such systems is obscene. I'm not suggesting yours is one, but how else would you combat spam?

Chris