Event ID: 1173 Source: MSExchangeIS Mailbox Store

1). In Exchange System Manager, right click the Store, click Properties. Then, copy the "Exchange database" path in the Database tab. For your information, my path is: E:\Program Files\Exchsrvr\mdbdata\priv1.edb.
2). Dismount the Store.
3). Click Start -> Run, type "cmd", and press Enter.
4). Use the "cd" command to enter the following directory "E:\Program Files\Exchsrvr\bin".
5). Enter the following command and press Enter:
esetuil /d "E:\Program Files\Exchsrvr\mdbdata\priv1.edb".
For your information, a successful output is similar to the following information:
   Initiating DEFRAGMENTATION mode...
   Database: E:\Program Files\Exchsrvr\mdbdata\priv1.edb
   Streaming File: E:\Program Files\Exchsrvr\mdbdata\priv1.STM
   Temp. Database: TEMPDFRG2880.EDB
   Temp. Streaming File: TEMPDFRG2880.STM
   Defragmentation Status (% complete).
6). Mount the Store again".