i'm not sure why you're taking offence. to me it seemed clear that mxlookup differs from the algorithm in section 5 of 2821 and what other mailers do. the rfc doesn't say that we need to abort of the mx lookup fails. i think this is important because it's possible for an mx lookup to fail and an a/a6 lookup on the same name return results. i had quite a bit of trouble with this when using level-5's dns last year. in addition, a quick inspection of postfix' src/smtp/smtp_addr.c seems to confirm that they perform a/a6 lookup on mx lookup failure. since other smtp agents don't notice the misconfiguration, we are left to find it.
anyway, i put the effort into pulling together my notes from last year on this to help, not to annoy. hopefull this information is not a further annoyance. - erik
