Applies to: Exchange Server 2010 SP3, Exchange Server 2010 SP2

Topic Last Modified: 2010-07-22

For optimal performance, there is a maximum number of concurrent sessions that a Client Access server can support. Microsoft Exchange Server 2010 imposes limits on the number of concurrent service sessions per user. The limits are set in several different ways. For some client interactions, limits are set for the maximum number of concurrent threads per server or the maximum number of sessions per server. For other client interactions, the limits are set for the maximum number of user sessions per server. Limits are set to improve performance, to prevent users from being locked out of e-mail access, and to prevent service disruption.

Session Limits by Client Type

The following table lists the maximum number of service sessions that are allowed per user for the different client types and services in Exchange 2010.

Client type Maximum user sessions per server

Exchange ActiveSync

16

Availability Service

16

Exchange Web Services

16

Exchange Management Console

16

RPC Client Access

32

Outlook Web App

16

POP3/IMAP4

16

Unified Messaging

16