Exchange Error – JET_errKeyDuplicate Illegal Duplicate Key

Avatar    Jarvis Flores     Updated On - 24 Jan 2019

Microsoft Exchange Server database file when gets corrupted then various JET engine errors occur depending on the cause of database file corruption. Most of the JET engine errors can be resolved by executing eseutil.exe, a built-in Exchange Server utility to resolve common MS Exchange Server database related errors. The utility checks the database file for fixing errors. However, some of the JET engine errors cannot be fixed by using the eseutil.exe utility. One of such JET errors is:

-1605 0xFFFFF9BB JET_errKeyDuplicate Illegal duplicate key 4294965691

When the aforementioned error message occurs, you cannot continue working with MS Exchange Server. The specified error message and the situation generally arises when the Eseutil tool recreates B-trees inaccurately.


This error cannot be fixed by using Eseutil.exe tool. In fact, if you keep trying the Eseutil.exe tool even after getting this error message, it may result in the loss of data and time, and would merely exaggerate the problem. In such a situation, an absolute backup of your Exchange Server database can be an ideal help. You can easily restore your database from the backup and save your time and data.

Exchange Server experts always recommend creating complete backup of the Exchange Server database files so that when JET errors occur, you can easily recover data. If you have complete backup of the damaged Exchange Server database file then by restoring the backup, you can restart working with Exchange Server without any data loss. But, in case you do not have any backup, you need to take help of third-party Exchange Recovery software.

An EDB Recovery software completely scans the damaged Exchange Server database file and repairs it. After the software completes the scanning process, it saves the recovered data on a user defined location. Kernel for Exchange Server recovery is such a third-party software, which has been designed to provide you a complete Exchange Server database recovery solution. The software supports almost all versions of MS Exchange Server ranging from Exchange Server 5.0 to 2016.