By default, Microsoft Exchange Server creates a queue directory in \Program Files\Exchange that it uses to process SMTP email bound for local delivery. Because this queue folder is created on the same drive as Exchange Server and the operating system, it can sometimes cause disk performance problems.
If you have heavy email traffic, the local delivery queue will generate a lot of disk activity that competes directly with the disk activity needed by the rest of the operating system and Exchange Server.
A high volume of email traffic added to intense system activity can cause the SMTP mail queue to perform slowly. There's only so much disk I/O to go around, and the disk's physical geometry may limit things even further.
If you're dealing with a particularly busy email system, one way to alleviate some of the load is to move Exchange Server's local delivery queue directory to another physical drive that isn't as busy:
- Go HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\
MSExchangeIS\ParametersSystem in the registry.
- Edit the Working Directory REG_SZ value to use another drive and path.
- Restart Exchange Server.
Note that when you do this, the local delivery queue directory in question should already be created.
Make sure that the new directory will not be scanned by antivirus software; you may need to manually exclude the new queue folder to guarantee this.
Finally, this isn't something you should do casually. If there isn't a lot of I/O contention on the disk where the queue is located, there's probably no immediate reason to relocate it. You can always move it back to its original location if it proves to be problematic though.
About the author: Serdar Yegulalp is editor of Windows Insight, a newsletter devoted to hints, tips, tricks, news and goodies for all flavors of Windows users.
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Related information from SearchExchange.com:
Tip: Disk performance best practices for MTA and SMTP queues
Tip: Stay above the SMTP queue floods
Tip: Command-line SMTP queue management for Exchange Server
Step-by-Step Guide: How to analyze SMTP log files in Microsoft Excel
Best Practices Guide: Optimizing Exchange Server disk performance
Reference Center: SMTP tips and resources
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