Enterprise Vault archiving tasks experience connection issues with Exchange targets

Problem

Enterprise Vault Exchange mailbox, journal, and public folder archiving tasks experience connection issues. This generates error messages in the event logs, and the tasks sleep unexpectedly. This issue is more likely to occur on Enterprise Vault servers that host multiple Exchange archiving tasks.

This issue arises from changes to the handling of session limits on the mailbox server in Exchange.

Error Message

From any of the Exchange archiving tasks, on the Enterprise Vault server:

Log Name: Veritas Enterprise Vault
Source: Enterprise Vault
Event ID: 3231
Task Category: Archive Task
Level: Error
Computer: vault.EV.local
Description:
Could not get a MAPI session from the session pool.

Error: <0x8004011d>
Source: Exchange Mailbox Archiving Task for E15MBX
Additional Information: Whilst processing user /o=First Organization/ou=Exchange Administrative Group (FYDIBOHF23SPDLT) /cn=Recipients/cn=83d0a43be73847b3bbaf4e7a96530b24-d1-1

V-437-3231

Log Name: Veritas Enterprise Vault
Source: Enterprise Vault
Event ID: 3419
Task Category: Archive Task
Level: Warning
Computer: vault.EV.local
Description:
Could not access Exchange Server. The dispenser will queue the current item and sleep for 60 seconds. Task: Exchange Mailbox Archiving Task for E15MBX

 V-437-3419

From the Exchange journal archiving task, on the Enterprise Vault server:

Log Name: Veritas Enterprise Vault
Source: Enterprise Vault
Event ID: 3237
Task Category: Journal Task
Level: Error
Computer: vault.EV.local
Description:
An error occurred opening the Journaling mailbox /O=FIRST ORGANIZATION/OU=EXCHANGE ADMINISTRATIVE GROUP (FYDIBOHF23SPDLT)/CN=RECIPIENTS/CN=D7B82AB3C94A4CA0BACDE258C8D31E29-JOURN

Check that the message store is available and the mailbox is accessible

 V-437-3237

Log Name: Veritas Enterprise Vault
Source: Enterprise Vault
Event ID: 2910
Task Category: Journal Task
Level: Error
Computer: vault.EV.local
Description:
An error in CArchivingAgent::SetupAndCallQueueMsg() occurred whilst creating the objects that are needed.

V-437-2910

On the Exchange mailbox server:

Log Name: Application
Source: MSExchangeIS
Event ID: 9646
Task Category: MAPI
Level: Error
Computer: mbx.EV.local
Description:
Mapi session /o=First Organization/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=57cbb5977c114cd099fc16d2d3ea5767-sysmb with client type MoMT exceeded the maximum of 32 objects of type Session.

Cause

By default, the maximum number of objects per session for a user is 32.  

Solution

Option 1

Use the Maximum Allowed Sessions Per User registry key to increase the number of allowed MAPI sessions per user, including the Vault Service Account.

Warning: Incorrect use of the Windows registry editor may prevent the operating system from functioning properly. You should back up the registry and your data before you make registry changes.

1. On the Exchange server, create a new registry DWORD value called Maximum Allowed Sessions Per User under the following registry key:
   
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem
    
2. Set Maximum Allowed Sessions Per User to a decimal value that will allow for all required sessions to connect.

Note: There is no specific upper-limit to this setting beyond the limits that are imposed by it being a DWORD.

For more information, see the following page on the Microsoft website: https://learn.microsoft.com/en-us/exchange/architecture/mailbox-servers/managed-store/managed-store-limits?view=exchserver-2019

Use the following formula to determine the maximum allowed sessions per user. This is only a guide and it may be necessary to increase the limit further. The formula does not make allowance for Discovery Accelerator, Compliance Accelerator, or Custodian Manager. The final value created will be the decimal value to be set. 

A = Number of mailbox archiving tasks × Number of connection threads (per task) × 4
B = Number of journal archiving tasks × Number of connection threads (per task) × 4
C = Number of public folder archiving tasks × Number of connection threads (per task) × 4
D = Number of Enterprise Vault servers with task controller service running × 20
E = Number of Enterprise Vault servers with storage service running × 32
F = Number of Enterprise Vault servers with shopping service running × 32
G = Number of Enterprise Vault servers carrying out PST migrations × 20

Total = 2 × (A + B + C + D + E + F + G)

Option 2

Configure each Exchange archiving task to run under a different user. This means that the 32 MAPI session store limit per user should not be reached because each task has its own 32 session limit, rather than sharing a single 32 session limit.

1. Stop all Exchange archiving tasks.
    
2. For each Exchange archiving, mailbox, journal, and public folder task, create a new user with an Exchange mailbox.
    
3. Grant each user the required Enterprise Vault and Exchange Server permissions using the Enterprise Vault documentation.
    
4. Go to each Exchange archiving task's Log on tab.
    
5. Click Use this account.
    
6. Enter the newly created user account to be used for the task.
    
7. Enter the password for the user account.
    
8. Click OK to commit the task properties changes.
    
9. Restart the Exchange archiving tasks.