I use a lot of space on the Exchange 2003 Server. It seems when I delete a large mailbox or cleanup old e-mail using system manager, it does not free up used hard drive space in proportion to the size of deleted messages. What should I do?
You're correct. Shrinking any database is a very costly operation, so most vendors avoid doing this at all costs. Exchange is no different. When you delete a large mailbox your database won't shrink in size at all. Essentially, you can think of the database size as remaining at the "high water mark" even after data has been deleted. This results in a certain amount of "white space" or empty space, existing inside of the database.
In order to "lower the high water mark" or reduce the size of the white space, you'll want to schedule a maintenance...
window for your Exchange server and run the ESEUTIL /D command on your database. This will shrink your database and reclaim white space.