Causes

• The Exchange administrator account doesn’t have sufficient permissions to open user mailboxes.
• This error code can also occur if your Exchange server exceeds the MAPI session limit during a migration.

Fixes

Step 1: Create A New Administrator User

Create a new administrator user on Exchange and give the account full mailbox access for all user accounts.

Step 2: Use New Account For Migration

Then, use the new account for the migration. You can delete the new administrator account after the migration is complete.

Step 3: Ensure File Not Password Protected

If you’re using PST files for the migration, ensure the files aren’t password protected.

Step 4: Adding Configurations To GSMME

You can resolve the issue (2nd cause) by adding configurations to GSMME or your Exchange server. For details, refer the GSMME Admin Guide.