Exchange Server 2010 mailbox databases grow in size as the data within them grows. But they will never shrink when data is removed from them.
Your options to reclaim that space are to either:
Create a new mailbox database and move all the mailboxes to that database
Perform an offline defrag of the existing database to shrink the file
The first thing to be aware of when planning a defrag is that you can only perform this task when the database is dismounted. That means during the process, no mailbox access.
The second thing is that you need some available disk space to perform the defrag.
Go to the Database Folder
cd e:\Exchange server\ Databases\DB01\
Dismount the Disk
Run the Eseutil for defrag
eseutil /d DB01.edb /t e:\defrag\temp.edb
As you can see, I got E driver where my DB is and I got an empty drive which is E where I will keep temporary database
Make sure that E drive has more space than your DB size
Once the defrag is completed, Mount the DB back