SBS - Exchange Email Spam Issue - Error Workaround - Exchange may not be retrying!

In the process of searching for the version numbers for the Exchange SMTPSVC for the previous blog post on using the wizards, we stumbled on what could be a big thing.

Yesterday, we posted about our experiences with two SBS servers, one our client's server and one ours, that seemed to drop email off the planet when hitting a hosting provider's SMTP server that Greylists. SBS - Exchange Email Sam Issue with Question to You.

Not sure how, but in our searches we came up with this:

andy webb View profile More options Mar 17, 2:07 pm
Something I haven't tried yet, but was talking with someone about last week was setting the Glitch Retry registry key. It's possible this isn't correctly being defaulted in SP2 or some version of SMTP.

In HKLM\System\CurrentControlSet\Services\SMTPSVC\Queuing, create "GlitchRetrySeconds" as a dword and try a value of 60 or 120. Then restart the SMTP service.

By default, messages receiving a 4xx SMTP response are processed as a "glitch" 3 times before being put back into the queue for processing on the retry interval. It seems like something in this mechanism is failing. [Emphasis ours] So, if assertively setting GlitchRetrySeconds to a value that allows the greylisting conditions to be satisfied, voila, a solution.

This is referenced a couple places:
http://technet.microsoft.com/en-us/library/aa998772.aspx
http://msexchangeteam.com/archive/2005/04/04/403297.aspx

This quote is from microsoft.public.exchange.admin via Google Groups: Exchange-->Greylisting. It is about three quarters of the way down.

This lead to another post on that newsgroup: Greylisting Problem. Here we see that there are indeed others having issue with Exchange not retrying if it receives a 471 Retry from a Greylisting server.

And then, a confirmation that Exchange indeed didn't retry as it should: Nabble.com: Does Microsoft Exzchange Exchange retry delivery correctly?

Now, given our experience working with the hosting company this afternoon and being able to repeat the problem, me thinks the problem is indeed in our court. That is, in Exchange.

As mentioned in the above quote, there is a registry key that needs to be added. From there, restart the SMTP service and hope! :D

So folks, time to get in touch with our clients and get that change in place!

UPDATE: And one more thing: My apologies for the original assumption that our SBS Exchange servers were not at fault. That is the assumption made when we first started into this stuff. And, it looks as though that assumption was dead wrong.

UPDATE 2008-06-18: Fixed the broken link in the TechNet Library referral.

Philip Elder
MPECS Inc.
Microsoft Small Business Specialists

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