Action: Test mail flow Before data migration to Office 365, confirm mail flow is working in both directions for user mailboxes ...

Action: Test mail flow Before data migration to Office 365, confirm mail flow is working in both directions for user mailboxes and distribution groups. Move a few pilot users and confirm the auto-forwarding is working as desired before velocity migrations. When ready to begin data migration, assign each user an Exchange Online license and set the auto-forwarding for the Office 365 mailbox to point to the routing domain (for example, pilot.contoso.com). The MX should point to G Suite. The FastTrack team can then begin backfill replication during the initial sync. The initial sync includes all old emails (not including emails between 30-60 days old) and can be scheduled T-21 days in advance of the planned cutover. The second pass controls the cutover date and time and includes email and calendar items between 30-60 days old. The migration team disables auto-forwarding on the Office 365 mailbox after the second cutover pass completes.  They also set G Suite auto-forwarding to point to Office 365. Contact your FastTrack team for more information.