2013-05-13 08:01:55 UTC
Postfix's documentation quotes for 'reject_unknown_helo_hostname':
"Reject the request when the HELO or EHLO hostname has no DNS A or MX
Under '3.6 Domains' of RFC 2821 it says:
"Only resolvable, fully-qualified, domain names (FQDNs) are permitted
when domain names are used in SMTP. In other words, names that can
be resolved to MX RRs or A RRs (as discussed in section 5) are
permitted, as are CNAME RRs whose targets can be resolved, in turn,
to MX or A RRs."
I have seen in Postfix's documentation that it caters for 'home-grown'
software for some attributes. Catering for POS software isn't being
As it is a requirnment for a RFC 2821 compliant SMTP server to have a
resolvable A and MX record, then 'reject_unknown_helo_hostname'
shouldn't even exist, instead Postfix should be rejecting the connection
Assuming this is why 'reject_unknown_helo_hostname' exists; the
home-brewer should get his software right, instead of expecting others
to make exceptions for his lack of skill.
If Postfix was compliant with RFC 2821 in this respect, I wouldn't have
had to of wasted half my day. This is the whole point of standards.