In order to apply an unrestricted throttling policy in Exchange 2013, open the Exchange Management Shell and issue the following three cmdlets:
New-ThrottlingPolicy UCCSPolicy
Set-ThrottlingPolicy UCCSPolicy -RCAMaxConcurrency Unlimited -EWSMaxConcurrency Unlimited -EWSMaxSubscriptions Unlimited -CPAMaxConcurrency Unlimited -EwsCutoffBalance Unlimited -EwsMaxBurst Unlimited -EwsRechargeRate Unlimited
Set-Mailbox <ServiceAccountName> -ThrottlingPolicy UCCSPolicy