Monday, April 25, 2011

Message Dehydration isn't a good thing for Exchange!

Ehlo All,


Quote of the week: "limit is 94% before message dehydration occurs."

A normally very stable client's Exchange Server 2007 stopped processing inbound emails and this was the issue above. Client reported all internal email was working though. I logged into their Exchange Server and reviewed the normal issues inside the Exchange Management Console and nothing jumped out (e.g. databases mounted, 3GB free space on C, 700GB+ free space on database partition (D), no quota limits, receive connectors present/enabled, etc). Strange. I decided to check the email filtering solution in front of the Exchange Server. Since I always recommend clients use my company's email filtering service (SpamCop - I'll discuss this is another post) since it allows me to quickly troubleshoot issues and provide very secure email service. Reviewing SpamCop outbound queue to the client's Exchange Server illuminated the error:


Deferred: : host 55.55.55.55 said: 452 4.3.1 Insufficient system resources (in reply to...

More details about this error can be found on this posting. Checking the client's Application Event Log for this error, I found it "The Microsoft Exchange Transport service is rejecting message submissions because the available disk space has dropped below the configured threshold.". Which was surprising since the C drive had a decent amount of space available (3GB+). What changed? Good old SBS's Windows Server Update Services had downloaded every update under the sun and the storage space threshold was passed and triggered back pressure. I uninstalled WSUS and that eliminated 10GB and back pressure was eased and email flow started. I plan to remove some other functionality as well and plan to do a scheduled reboot as well to free up more space. To sum up, SBS causes more problems than it's worth for Exchange deployments. I prefer clean Exchange installs over Exchange SBS installs.

-Ben

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