Hello Olle,
CmisSync is compatible with all CMIS servers.
But Microsoft has yet to enable CMIS on 
Office365.
If you really want to use CmisSync with 
Office365, here are two things that I recommend doing:
1) Give 3 votes to this idea on Microsoft 
Office's official uservoice: 
https://officespdev.uservoice.com/forums/224641-general/suggestions/6003155-implement-cmis-for-realAlso enter a comment describing why you need CMIS.
And
 ask your colleagues to do so as well. Some people at Microsoft are 
really looking at this page, so posting there is actually useful.
2) Call your Microsoft representative and demand that they implement CMIS.
CMIS is actually already built into 
Office365, research shows that they voluntarily disabled the feature, thinking people would not use it.
So
 it is not that hard for Microsoft. If Microsoft salespeople get asked 
about CMIS enough, they will ask their technical team to re-enable it.
CMIS would allow you to use not only CmisSync but also a wide array of other CMIS clients.
Best regards,
Nicolas Raoul
CmisSync team
Aegif