Exchange Throttling Policy

On-premise Exchange uses throttling policies to ensure that a single user does not use up all the Exchange server resources. Normally, this ensures that the Exchange server remains healthy and available for all the users. However, during migration, if you migrate more mailboxes at a time, the Exchange server will throttle, and you will encounter performance issues. Exchange throttling imposes a limit on the number of concurrent call requests that can be executed at the same time. Therefore, it is advisable to create a new "migration" throttling policy in order to achieve error free migration.

EdbMails application is designed to migrate the email and other items granularly to avoid throttling issues. In addition, you can create a custom throttling policy with limits higher than the default ones or even disable these limits and assign it to the user account used in the EdbMails application to perform the migration.

Steps to create custom throttling policy in Exchange Management Shell (EMS)

1. To set the limits higher

   Verify the current throttling

   Command: Copy & Paste it on EMS

   Get-ThrottlingPolicy | fl

2. Create a new throttling policy:

   Command: Copy & Paste it on EMS

   New-ThrottlingPolicy

3. throttling policy settings.
   Use $null or Unlimited values to disable the limits or use custom values

   • Exchange Server 2010:

     Command: Copy & Paste it on EMS

     Set-ThrottlingPolicy NewPolicy -RCAMaxConcurrency $null -EWSMaxConcurrency $null -EWSMaxSubscriptions $null -CPAMaxConcurrency $null

   • Exchange Server 2013 and newer:

     Command: Copy & Paste it on EMS

     Set-ThrottlingPolicy NewPolicy -RCAMaxConcurrency Unlimited -EWSMaxConcurrency Unlimited -EWSMaxSubscriptions Unlimited -CPAMaxConcurrency Unlimited -EwsCutoffBalance Unlimited -EwsMaxBurst Unlimited -EwsRechargeRate Unlimited

   • Assign the admin account used in EdbMails application to the throttling policy

     Command: Copy & Paste it on EMS

     Set-Mailbox "mailbox name" -ThrottlingPolicy NewPolicy

   • Assigning the throttling policy to all users in your organization

     Command: Copy & Paste it on EMS

     Set-ThrottlingPolicy "NewPolicy" -ThrottlingPolicyScope Organization