Review of the Enterprise Vault (EV) event log reports the following:
Log Name: Veritas Enterprise Vault
Source: Enterprise Vault
Date: 10/26/2021 12:22:07 PM
Event ID: 2304
Task Category: Agent Client Broker
Level: Error
Keywords: Classic
User: N/A
Computer: evserver.veritas.com
Description:
Failed to lookup Message Queue name for the Retrieval Agent in the Directory Service on computer EVSERVER
Possible Reasons:
1. Failed to connect to the Directory Service
2. Failed to find Task entry : 1D536AEE21CE2304E89795C6534BE78051012000evserver
How to purge Microsoft Message Queues (MSMQ) used by Enterprise Vault
https://supportenterprisevault.cloud.com/support-home/kbsearch/article?articleNumber=100016906
This issue is caused by corruption of the EV Exchange Mailbox Arching Task Retrieval Agent and associated MSMQs after a server migration and subsequent upgrade to version 14.1.1.
1. Stop the Exchange Mailbox Archiving Task. Right click on task and select Properties to view and document the Settings tab for the System Mailbox and Schedule tab settings, see image below:

2. Open Computer Management, expand Services and Applications, expand Message Queuing and select Private Queues, see image below:

3. In the right window you will see the MSMQs for Exchange Server Archiving Task (A1-A7).
Note: If these MSMQs have items refer to the Related Articles below on how to purge these queues correctly.
4. Select and right click on each individual MSMQ queue and then select Delete. Repeat the process for A1 through A7 queues, see image below:

5. Once all MSMQs for the Exchange Mailbox Archiving Task have been deleted then delete the corresponding task in the Vault Administration Console (VAC).
6. Create a new Exchange Mailbox Archiving Task with appropriate System Mailbox and Schedule settings and test retrieval of an archived item.
