As stated previously, there is no direct upgrade path between Dynamics CRM 4.0 to 2013 with the Outlook Client. As such, after upgrading to CRM 2011 from 4.0, users can upgrade to 2013 as explained in this section.
Microsoft does not require a client upgrade of the CRM for Outlook client for Dynamics 2011 when using Dynamics CRM 2013, but the following conditions apply:
You must be on Microsoft Dynamics CRM 2011 Update Rollup 12 or later.
Even though Update Rollup 6 is officially supported, it is not recommended since newer updates have added significantly increased stability and ...