MAPI_E_LOGON_FAILED - Configuring NSPI Connection Limit (4261961)

MAPI_E_LOGON_FAILED

Directory Services event log when this issue occurs:

"NSPI max connection limit for the user has reached.

You need to do NSPI unbind on old connections before making new connections."

Possibly have to enable Active Directory diagnostic event logging to see NSPI limitation log entries.

Important: This step must be performed only if you have any Windows Server 2008 or later domain controllers acting as Global Catalog.

By default, the maximum number of simultaneous Name Service Provider Interface (NSPI) connections equals to 50 per user for Windows Server 2008 or later domain controllers. Therefore, to avoid possible issues related to exceeding that value, you may need to increase the NSPI connection limit on all Windows Server 2008 or later domain controllers acting as Global Catalog. The recommended limit value equals the number of agent instances working simultaneously multiplied by 5.

To change the default connection limit for a domain controller, take the following steps:

Click Start, click Run, type regedit, and then click OK.

Locate and then click the following registry subkey: 

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\NTDS

Click the Parameters key.

On the Edit menu, point to New, and then click DWORD Value.

Type NSPI max sessions per user, and then press Enter.

Double-click NSPI max sessions per user, type the appropriate maximum number of the NSPI connections, and then click OK.

Restart the computer or restart Active Directory Domain Services.