Office 365 Connector is mainly used in conjunction with ARS Add-on so ARS can provision user mailboxes, groups and contacts from your on-premises Active Directory into the cloud.
But there are some scenarios which are not covered by ARS Add-on such as synchronization of external contacts (Contact Object in Office 365 Connector).
To cover this scenario we need Workflow which will provision contacts in Office 365 from AD, csv-file or other source.
In my case I used ActiveRoles Connector as source. Below attributes are required to create an external contact in Office 365:
After sync we can check Offline Global Address List to see imported users.