It is possible to run the CRM server and the Outlook clients at different rollup levels. However, this is not recommended and not best practice. Reason being, there may be a fix for a specific issue that requires the fix to be installed on both the CRM server
and the Outlook client. You may also notice some strange things happening due to the mismatch of the rollups.
I would suggest adding the rollup to one of the Outlook clients and then trying to determine why there is slower performance on the Outlook client, and if there is anything that can be done to speed it up such as allowing more simultaneous downloads, checking
mailbox size and how full it is, etc.
Jason Peterson