How often should I defragment an Exchange data store?

Microsoft Exchange best practices recommend that you perform complete offline defragmentation and optimization of information stores once every three months. You should probably schedule this into an annual maintenance cycle and—where necessary—provide ample warning to administrators and end-users alike when the scheduled time comes.

Microsoft Exchange automatically handles database cleanup as part of its core daily maintenance routines, but this functionality does not recover disk space. To recover disk space, you must schedule a defragmentation pass of Exchange data stores.