Jaroslav Skarvada:
> Hi,
>
> the postconf(5) documentation for reject_invalid_helo_hostname reads:
> > Reject the request when the HELO or EHLO hostname syntax is invalid.
>
> This seems ambiguous as it can be interpreted different ways:
> 1) 'HELO hostname' / 'EHLO hostname' syntax, i.e. HELO / EHLO syntax
> 2) hostname syntax for HELO / EHLO
SMTP syntax is specified in RFC 5321. If the client sends HELO,
EHLO, MAIL or RCPT without a required command parameter, then that
is an SMTP syntax error. The SMTP syntax error reply code is 501
as specified in RFC 5321.
Hostname syntax is specified in RFC 952 and 1123. If the client
specifies an invalid name in HELO or EHLO, then that name may be
rejected with reject_invalid_helo_hostname. This has a configurable
reply code, like other like other main.cf reject_mumble actions for
HELO, EHLO, MAIL, RCPT, etc., commands.
Wietse
