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Re: Weird DNS issues for domains

  • From: Todd Vierling
  • Date: Thu Sep 29 13:31:06 2005

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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