We migrated our on-premises Exchange 2010 mailboxes to Office 365, and synchronized our Active Directory. I'm the admin of the Office 365 tenant.
Now my users are using Outlook 2010 and 2013 and are trying to share their calendars with each other, with full details, using the button show below (excuse the Dutch language version of Outlook 2013). This button pops up a new mail message where one can share their own agenda and/or request access to one or more recipients' agendas.
Giving the recipient Free/Busy permissions works fine. Anything higher, such as 'limited details' or 'full details' fails when one tries to send the message. The following window appears (again, in Dutch):
This message essentially says it's not allowed by policy to assign permissions of this level to one or more of the recipients.
The weird thing is, that manually editing the permissions via the right-most button works fine. I can give a user Reviewer permissions without a problem. My users are however used to the other method and I'd prefer both to work.
What policy is it talking about and where do I change it? The only related thing I found is the "Default Sharing Policy", but this appears to deal exclusively with sharing to external users!