On Wed, 13 Jun 2012, Matt Simerson wrote: > https://github.com/smtpd/qpsmtpd/pull/29
I consider this statement to be troublesome also: Per RFC 2821, the HELO hostname must be the FQDN of the sending server or address literal. RFC 2821 doesn't say "must". It says neither should nor must, but simply The argument field contains the fully-qualified domain name of the SMTP client if one is available. Mail servers can certainly be expected to have a FQDN. But expecting them to have *only one* FQDN may be too tight a constraint. Is there a definition of canonical FQDN? Is the canonical FQDN anything other than just the name defined by whoever manages reverse DNS? In my experience, reverse DNS is frequently managed (or, frequently, not managed) by an ISP, not by the admin of the mail server.
