Event ID 2002 on Exchange 2013 (MSExchange Front End HTTP Proxy)

I get a warning message "[Eas] The number of outstanding proxy requests for mailbox server xxxxxxxx has exceeded the max limit 5000. Current request will be rejected." on all cas server and I  also create "Maximum Allowed Service Sessions Per User (value = 10000)" to "HKLM\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem" but It's not worked.

I must restart cas server for troubleshooting.

Please Help me. 

P.S. Exchange 2013 SP1 (Version 15.0 (Build 847.32))