The rollup provides the following fixes and improvements (https://support.microsoft.com/en-gb/help/4295699/update-rollup-22-for-exchange-server-2010-service-pack-3)
4295751 – EWS impersonation not working when accessing resource mailboxes in a different site in Exchange Server 2010 SP3
You can download this rollup from https://www.microsoft.com/en-us/download/details.aspx?id=57065
