In order to use Exchange Online you need at least Outlook 2016.

1. Notify: You or your manager will be contacted when its time to move to Exchange Online.
2. Software Requirements:We will make sure you are using the latest version of Microsoft Outlook. Currently Outlook 2016 is the most recent. Outlook 2016 is the preferred client for Exchange Online. If Outlook 2016 is not possible then you will be limited to using OWA.
3. Delegates: Let us know if you have any delegate access to anyone’s mailbox or calendar, or if you have delegates connecting to you. Delegates will be required to move with you to Exchange Online. We move whole departments at the same time and this is usually covered automatically.
4. Shared Mailboxes:Let us know if you access any shared mailbox’s or resources. These mailboxes will need to be converted to shared (if not already that type) and  then moved during your migration.
5. Distribution Lists:  Let us know of any distribution lists that you manage.  These lists will need to be migrated with your account.
6. Special Permissions: Let us know if you have SendAS or Full access to any mailboxes. The same requirements apply as  #3 above. Those resources or mailboxes will need to be moved at the same time.