Crist Clark <crist.clark@globalstar.com> wrote: [...]
The problem I've seen is when an SMTP server does not accept emails which have non-resolvable MAIL FROM domain. When the sender is a dumb SMTP client, not an MTA, this can cause problems.
Well, that "dumb SMTP client" should stop pretending to be a MTA then. If it can't queue and retry, it shouldn't even *think* about looking for MX records. Besides, what sort of "dumb SMTP client" did you have in mind? Formmail scripts? Worms? Outlook Express? I can't say I'd miss mail from any of those.
(I noticed this happen to a high traffic customer who had both of their DNS servers in the same /24 located in Slidell, LA. Needless to say, they were down for more than a few hours when Katrina rolled through.)
Having reachable DNS isn't going to help anyway if the MX host is also unreachable for an extended period. Mail is still going to bounce after a few days if somebody doesn't fiddle with DNS. -- 'Twas a woman who drove me to drink, and I never had the courtesy to thank her for it. - W.C. Fields