sendmail, 4th Edition

Spam Suppression Features

As spam and phishing problems become more and more pervasive, sendmail has added more features specifically targeting those problems:

• The FEATURE(badmx) (FEATURE(badmx)—V8.14 and Later on page 291) rejects any client hostname, the domain part of which resolves to a bad MX record (V8.14 and later).

• The FEATURE(block_bad_helo) (FEATURE(block_bad_helo)—V8.14 and Later on page 292) rejects clients who provide a HELO/EHLO argument which is either unqualified (lacks a domain part) or one of the server’s names (V8.14 and later).

• The FEATURE(greet_pause) (FEATURE(greet_pause)—V8.13 and Later on page 293) suppresses slamming attempts (V8.13 and later).

• The experimental FEATURE(mtamark) (FEATURE(mtamark)—V8.13 and Later, Experimental on page 295) implements the MTA mark proposal (V8.13 and later).

• The FEATURE(require_rdns) (FEATURE(require_rdns)—V8.14 and Later on page 296) rejects clients whose IP address cannot be properly resolved (V8.14 and later).

• The FEATURE(use_client_ptr) (FEATURE(use_client_ptr)—V8.13 and Later on page 297) causes the connecting client’s IP address to be screened early even if the FEATURE(delay_checks) is used (V8.13 and later).