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Date: Thu, 29 Sep 2005 13:29:13 -0400 (EDT) From: Todd Vierling <tv@duh.org> To: John Dupuy <jdupuy-list@socket.net> Cc: nanog@nanog.org In-Reply-To: <6.0.3.0.2.20050929121444.053aa780@mail.socket.net> Errors-To: owner-nanog@merit.edu On Thu, 29 Sep 2005, John Dupuy wrote: > If you are talking about strictly http, then you are probably right. If you > are hosting any email, then this isn't the case. A live DNS but dead mail > server will cause your mail to queue up for a later resend on the originating > mail servers. A dead DNS will cause the mail to bounce as undeliverable. If a mail server is bouncing immediately on a DNS SERVFAIL (which is what you'll get when a remote DNS server is down), then that mail server is badly broken and will break quite a bit during tier1 failure situations. Failure to resolve != resolves to NXDOMAIN/empty. A failure to resolve (SERVFAIL) should result in the same queueing behavior that the remote SMTP server uses for failure to establish a TCP connection. -- -- Todd Vierling <tv@duh.org> <tv@pobox.com> <todd@vierling.name>
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