I have a SBS2011 server with Exchange 2010 with a few users configured. I have one user who has about 5 Exchange mailboxes configured in Outlook 2010 as separate Exchange accounts, NOT as "open these additional mailboxes". This was done to keep the local .ost file(s) smaller. Normally performance is fine, however periodically during the work day the user experiences an issue which normally manifests itself in an outgoing email hanging in the Outbox for a period of 5-15 minutes. During this time other users do not experience issues. It seems that when this happens a MSExchange ADAccess event 2915 is logged saying the user has gone over budget for component RCA. I'm not sure if the throttling is causing the Outlook issue, or if there is an underlying issue causing the Outlook performance issues and the 2915 event is a symptom, not a cause. Any thoughts?