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?
#2) I assume to pass the non_fqdn check it only has to be in the correct
format like somethingfake.com and not resolve or have DNS records.
Correct?
#3) When checking unknown_helo is it checking if the resolved IP matches
the client IP? Or just that it resolves to any IP?
#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?
