Once your Exchange mailbox has been migrated to the new server, you will need to make a configuration change on your mobile device to continue receiving email.
1. Open the email app.
2. Tap more. (Top Right)
3. Tab Settings.
4. Under Accounts, Tap the email address.
5. Scroll to the bottom. Tap Exchange server Settings.
6. In the Exchange server field, change it to, outlook.office365.com .