post...@ptld.com:
> Under smtpd_helo_restrictions there is
> reject_invalid_helo_hostname
> reject_non_fqdn_helo_hostname
> reject_unknown_helo_hostname
>
>
> #1) What is the difference between invalid and non_fqdn? In plain speak
> they sound the same to me. If its not fqdn isn't that malformed?
Non-fqdn form has no '.' between domain labels. It dates from the
days that rich organizations could not buy a top-level domain name
for themselves.
Invalid form violates domaih name syntax as required by RFCs.
In both cases, if the Postfix documentation does not mention DNS,
then DNS is not involved.
> #3) When checking unknown_helo is it checking if the resolved IP matches
> the client IP? Or just that it resolves to any IP?
Please RTFM Postfix documentation. If it does not mention IP addresses
then it does not use the IP addres,
> #4) If you use unknown_helo doesn't that encompass the other two checks
> so it would be redundant to use non_fqdn with unknown_helo?
DNS Lookups take more time.
Wietse
