It is well known that an Outlook client sending too many RPC connections per second could result in overall Exchange server performance degradation. It could be a desktop search engine, e-mail archiving products, custom apps written to manipulate exchange mailbox data… the list goes on.
In the past, the solution to this for Exchange administrators was limited. It is not practical at times to call the user who is causing too many RPC requests and wouldn’t it be better if the issue can be handled transparently?
Exchange Team answered that in Exchange Server 2007. The feature is called Client Throttling. RPC Client Throttling computes remote operation (ROP) statistics based on overall RPC average latencies. If high ROPs per second is detected (excluding short spikes) the back-off request is sent to the client.
For Outlook 2007 clients, a ropBackoff request is added to the back-off queue. ropBackoff is a new function in Outlook 2007 and earlier Outlook client do not understand this function.
Yes grasshopper, I know, I have the answer, patience!
For Outlook 2003 clients and earlier versions, the status code RPC_S_SERVER_TOO_BUSY is sent instead.
You can tune Throttling Factor using RPC Throttling Factor registry key. I can write a lot but I will instead send you to the great article written by great minds at Exchange Team. If you read this article, I promise, you will not be disappointed.
It must be satisfying when you say back-off and they obey!