1. Log in to the D365 trial account.
2. Go to Advanced Settings, Administration, and System Settings.
3. Go to the Email Tab.
4. Select Process Email Using to Server-Side Synchronization.
5. Again go to settings, Advanced settings, Email Configuration, and select Mailboxes.
6. Select Active Mailboxes view.
7. Select the mailboxes that you want to test and enable.
8. On the command bar, select APPROVE EMAIL and then select OK.
9. Once approved, select TEST & ENABLE MAILBOX.
10. On the confirmation dialog box, select OK.
Thanks.!!