gmail - What's FSL_HELO_FAKE email spam penalty?

Question

question from:https://stackoverflow.com/questions/66064084/whats-fsl-helo-fake-email-spam-penalty

Answer 1

I found this article that generally describes it.

https://flylib.com/books/en/3.44.1.28/1/

From what I've gathered, it basically means that you are sending Gmails NOT FROM Gmail.

3.4.2 20_fake_helo_tests.cf

This file defines a set of rules that use the eval test check_for_rdns_helo_mismatch( ) . This test takes two arguments: a regular expression pattern to match against the reverse DNS lookup of the connecting client's IP address, and a regular expression pattern to match against the hostname provided by the client during in the SMTP HELO command. Spammers often use mail programs that forge the HELO hostname, and these tests look for such forgeries when the clients have hostnames that match those of major commercial ISPs. Here's an example of a test from this file:

 header FAKE_HELO_AOL  eval:check_for_rdns_helo_mismatch("aol.com","aol.com") describe FAKE_HELO_AOL  Host HELO did not match rDNS: aol.com 

This test matches if the client connects from an IP address that reverse-resolves to an aol.com hostname but claims in the HELO to have a hostname that does not match "aol.com". These tests are applied to all of the Received headers from untrusted relays.

You can use this eval test to reject messages that claim, in their HELO, to be from your own host.