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Re: BCP for handling DNS SERVFAIL results

2005-11-27 00:41:46

Valdis Klētnieks writes:
I think Arnt's meaning was "If you get a SERVFAIL trying to get the MX, then you *don't* know there's no MX, so dropping back to an A is improper. The message should be queued and retried later".


I'd say that SERVFAIL is best covered by RFC 2821 section 6.1, which has this to say about error handling: «It [the MTA] must take this responsibility seriously. It MUST NOT lose the message for frivolous reasons, such as because the host later crashes or because of a predictable resource shortage.» Although the DNS is not mentioned, the passage doesn't seem to condone speculatively falling back to A in case of an MX query timeout, SERVFAIL, or other uncertain response.