Currently I'm using Microsoft Dynamics® CRM Online Spring '14 (6.1.3.119) (DB 6.1.1.1847) and we have installed the CRM Email router 2013, we are planning to upgrade to Dynamics CRM 2015.
Can I upgrade the CRM Email Router 2013 to 2015 while using Dynamics CRM Spring 14?
I found a link to do that(https://technet.microsoft.com/en-us/library/dn531069.aspx#BKMK_Upgrade2013) but it doesn't say if is backwards compatible also the link to downoad the Email Router 2015 says you need "Microsoft Dynamics CRM 2015" https://www.microsoft.com/en-us/download/details.aspx?id=45017