If DNS fails, CheckHelo should not reject mail
Currently the CheckHelo Module checks if a FQDN is resolvable and handles various error states. But it fails to handle the error state "query timed out" and therefore returns "FQDN not resolvable", which means if DNS fails for whatever reason all mails get rejected.
So I propose the addition of an error handling for "query timed out" that does not return PROTO_ERROR or PROTO_REJECT, because without DNS we at least want to get mail.
This happened to us a few days ago when we had a DNS outage and we rejected all mails... I'd rather get lots of spam than reject lots of ham ;)