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Guest -> RE: Cannot send mail to certain domains (7.Oct.2004 11:21:00 PM)
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For anyone not following this thread closely, This issue is not an ISP problem. As of yet, I, nor anyone else posting here, has found a permanant solution to the core issue. (However I am aware of a work around)
Let me summarize There is a bug in Exchange 2003 that causes emails to randomly fail. I've personlly witnessed the exact same bug in 3 different companies. Using both 2003 SBS and 2003 Enterprise Editions.
The Problem is that Exchange 2003 sometimes fails when looking up an MX record, it then does an a record lookup..which, for some domains, return another ip address that doesn't support incoming mail. This results in the email bounce backs.
The Discovery/Work Around I stumbled across this work around, which supports the above diagnosis of the issue (also supported by previous posts to this thread) If you install a mail relay (non-exchange) and route the exchange email to it, and let the mail relay do the lookups it removes the exchange dns lookup bug from the equation. I stumbled across this when installing Trend Micro mail relay and GFI Mail Essentials 10 Mail Relay. Both Exhange boxes previously experiencing this issue stopped after the mail relays were implemented.
ConclusionUntil MS patches the bugged DNS lookup, i see the simplest workaround to be installing a mail relay to do the dns lookup instead of exchange.
hope this helps -Arthur griffonage@%nospam4me%gmail.com
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