We have Contact objects in Active Directory that are synchronized into Office 365. However, many of these are contacts for users that we have also established an AD account for, meaning we have two objects for many of these people. As we use SharePoint, we need both of these objects to be current (one for the address book, and one for SharePoint).
Exchange Online supports mail users (non-mailbox users), and in Exchange Online, mail contacts can be synchronized from AD contacts, so how do you synchronize a mail user instead of a mail contact? My understanding is that these would be Active Directory users that we just wouldn't license, and I assume we'd set a specific AD property that puts them in mail users instead of mail contacts, but I can't find any documentation about how to do this.