The side effects of low hard-drive space on any Windows application, including, especially, Exchange Server, shouldn't be ignored. Generally, when a system partition's free space falls below 100 MB, you should treat it as a serious problem.
Exchange Server in particular can exhibit strange behaviors if free space begins to plummet below a crucial level (the exact level depends on the amount of activity on the server, but again, 100 MB is a good baseline figure. Some behaviors include email sitting in outboxes and never being delivered, requiring a reboot for the delivery to take place, or excessive errors being registered in the system logs. Note that the system logs themselves take up space, and should not be allowed to grow without restriction.
Consistent system hygiene will usually alleviate this problem, but free space can vanish in unexpected ways. As before, there may be system logs that can be archived and moved offline, or there may be temporary files that need to be deleted to free up space (look in WindowsTemp). Within Exchange, you may also want to turn off any unneeded logging or tracking functions, such as Message Archival Logging and SMTP Protocol Logging, which are really only needed for debugging. If you have files in imcdatainArchive, imcdataoutArchive, and imcdataLogs, they can be safely deleted.
In extreme circumstances, you need to relocate the Mailroot directory, the repository for mail received through Exchange's SMTP service. The Mailroot directory is normally kept in Program FilesExchsrvrMailroot on the same partition as Exchange Server. Moving it to another partition or physical drive can significantly improve performance, especially if you have a great deal of outgoing SMTP mail traffic on the server. See Microsoft Knowledge Base article Q318230 for step-by-step instructions on this, as it is a fairly complicated procedure.
Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter.
Editor's Note: This tip originally appeared on SearchWin2000.com