Exchange 2010 – slow performance

Environment – CAS Array – with 2 CAS/Hub Transport servers. DAG with 2 MBX servers. All 2008 R2 servers

Issue – When users delete a large number of items in their inbox, the outlook client will hang on Synch Status "Updating"

On the Exchange 2010 CAS server – Slow performance logs will appear such as:

eventID 1050 – Source MSExchange Extensibility – Task Category MExRuntime
The execution time of agent 'Conversations Processing Agent' exceeded 90000 milliseconds while handling event 'OnPromotedMessage' for message with InternetMessageId: 'Not Available'. This is an unusual amount of time for an agent to process a single event. However, Transport will continue processing this message.

eventID 1050 – Source MSExchange Extensibility – Task Category MExRuntime
The execution time of agent 'Mailbox Rules Agent' exceeded 90000 milliseconds while handling event 'OnPromotedMessage' for message with InternetMessageId: 'Not Available'. This is an unusual amount of time for an agent to process a single event. However, Transport will continue processing this message.

EventID 14035 – Source MSExchange MailTips – Task Category MailTips
Process Microsoft.Exchange.InfoWorker.Common.Delayed`1[System.String]: MailTips query failed for mailbox SMTP:Username@doamin.com. Latency:OpenSession:82173, total:82173. The returned exception is: Microsoft.Exchange.InfoWorker.Common.Availability.TimeoutExpiredException: Request could not be processed in time. Timeout occurred during 'Getting-MailboxFull'.
. Name of the server where exception originated: Cas Server Name.

The CAS servers in the CAS array both have 8 gigs of ram, 2 CPUs, 64-bit, and are not over burdened for resources.

Not sure what is causing this issue, would it be the CAS servers talking to the backend MBX servers, or possibly an issue between outlookand the CAS servers?