Administrators sometimes encounter problems during the process of setting up the Client Access Server Role.

In 2007, Microsoft introduced a lot of new functionalities one of which was the Client Access Server Role. The Client Access Server Role is used to handle multiple client connections that can access a client’s mailbox. These client connections can be initiated from a variety of entry points such as: web browsers, mobile phones, various handheld devices, or from different email clients across the internet. The main benefit of the Client Access Server Role is that it is used to offload a large majority of the resource usage that is usually incurred by the Microsoft Exchange server. Additionally, it reduces the need to run extra services on the email servers for services associated with the external clients. This additional benefit is realized in increased security of the email server.

The Client Access Server Role can be combined with other roles on the Exchange server such as: the Mailbox, Hub Transport, and Unified Messaging roles. As with all new services and activated role functions on a new server, sizing of the various resources – processors, memory, disk drives, adapters, etc. – needed to support these new functions is always important. Undersizing of resource needed for the new services and functions can have undesirable consequences to say the least.

When considering the combination of roles on the mail server, administrators should be aware of the potential problems that can be created. One of the potential problems can occur if the Mailbox role and the Client Access Server role are combined. Specifically, the mailbox role may become exposed to risks as additional services are installed on the server. These additional installed services may have been considered or tested during the staging process by previous administrators or IT staff.

There are other problems that can occur when implementing the Client Access Server role.

It has been reported that if the server is hosting the Client Access Server role then there is a possibility that the MSExchangeSyncAppPool application pool will crash the server. Unfortunately not only can the server crash but the application can also become disabled after five times within five minutes if the default rapid-fail setting has been configured. Events are recorded in the system log such as the following:

Event ID 1011
Event Type: Warning
Event Source: W3SVC
Event Category: None
Event ID: 1011
Description:
A process serving application pool ‘MSExchangeSyncAppPool’ suffered a fatal communication error with the World Wide Web publishing Service. The process id was ‘<process id>’. The data field contains the error number.

Event ID 1009
Event Type: Warning
Event Source: W3SVC
Event Category: None
Event ID: 1009
Description:
A process serving application pool ‘MSExchangeSyncAppPool’ terminated unexpectedly. The process id was ’1948′. The process exit code was ’0×1′.

Event ID 1002
Event Type: Error
Event Source: W3SVC
Event Category: None
Event ID: 1002
Description:
Application pool ‘MSExchangeSyncAppPool’ is being automatically disabled due to a series of failures in the process(es) serving that application pool.

An Update Rollup 2 for Microsoft Exchange Server 2007 Service Pack 1 exists which when installed corrects this problem.

Another issue that can happen when running the Service Pack 1 setup for Exchange 2007 is that you may receive the following error messages:

Exchange Server component Client Access Role failed.
Error: Error:
Unable to create Internet Information Services (IIS) directory entry. Error message is: The system cannot find the path specified.
. HResult = -2147024893.
The system cannot find the path specified.

This can happen if the Exchange Server 2007 was installed with three roles: the Hub transport role, the Edge transport, and the Client Access Server role. It is possible that the Client Access Server role was not entirely dedicated to the server and the Hub transport server also had the same role. An administrator can correct this by removing the CAS role from the server as a temporary solution.

To remove the Client Access server role from the Exchange server follow these steps:

1. Select Start — Control Panel — Add/Remove Programs.
2. Find and select Exchange Server 2007. Click Remove. (The Exchange 2007 Setup wizard will start.)
3. Select Next. (A screen will be displayed which shows the Exchange 2007 server roles that have been installed.)
4. Deselect the checkbox associated with the Client Access role.
5. Click Next.

The setup wizard will then confirm that all prerequisites have been met and then remove all files associated with the Client Access Server role.