On 11/18/19 8:55 AM, Gregory Heytings wrote: > > Hi, > >> >> I know it’s an RFC violation, but I see no email that is delivered >> with a bare IP helo that is legitimate. >> > > That might be your experience, but RFC 2821 (3.6) and RFC 5321 (2.3.5 > and 4.1.4) explicitly state that an address literal can be used after > HELO/EHLO. So it's a RFC violation to reject mail for that sole reason. I don't believe the RFC has any MUST about the receiver having to accept any specific message of this kind, thus it isn't an RFC violation to reject it. (See your next comment quoting the RFC which admit that it is allowed (if discouraged) for a site to be selective on what mail it accepts. > >> >> How much legitimate mail do you get with an IP helo? >> > > Two other users replied to your question. For real-world mail > servers, my experience is that the only safe restriction (safe = no > false positives) is "reject_unknown_reverse_client_hostname". With > other restrictions, your users will never receive emails from > administrations, schools, hospitals, etc., not even in their spam > box. Rejecting mail is an extreme measure, see RFC 5321 (7.9): > "considerable care should be taken and balance maintained if a site > decides to be selective about the traffic it will accept and process." > > Gregory
-- Richard Damon
