Follow the steps below to implement Exchange On premise to Office 365 migration
Step 1: Create a migration endpoint
Prior to performing on-boarding and off-boarding remote move migrations in an Exchange hybrid deployment, we recommend that you create Exchange remote migration endpoints. The migration endpoint contains the connection settings for an on-premises Exchange server that is running the MRS proxy service, which is required to perform remote move migrations to and from Exchange Online.
Step 2: Enable the MRSProxy service
If the MRSProxy service isn't already enabled for your on-premises Exchange servers, follow these steps in the Exchange admin center (EAC):
Open the EAC, and then navigate to Servers > Virtual Directories.
Select the Client Access server, and then select the EWS virtual directory and click Edit Edit icon.
Select the MRS Proxy enabled check box, and then click Save.
Step 3: Use the EAC to move mailboxes
You can use the remote move migration wizard on the Office 365 tab in the EAC on an Exchange server to either move existing user mailboxes in the on-premises organization to the Exchange Online organization or to move Exchange Online mailboxes to the on-premises organization. Choose one of the following procedures:
Move on-premises mailboxes to Exchange Online
You can use the remote move migration wizard in the EAC in the on-premises Exchange organization to move existing user mailboxes from on-premises Exchange to Exchange Online:
In the EAC, go to Office 365 > Recipients > Migration.
Click Add Add Icon, and then select Migrate to Exchange Online.
On the Select a migration type page, select Remote move migration and then click Next.
On the Select the users page, click Add Add Icon and select the on-premises users to move to Microsoft 365 or Office 365 and click Add and then click OK. Click Next.
On the Enter the Windows user account credential page, enter the on-premises administrator account name in the On-premises administrator name text field and enter the associated password for this account in the On-premises administrator password text field. For example, "corp\administrator" and a password. Click Next.
On the Confirm the migration endpoint page, verify that the FQDN of your on-premises Exchange server is listed when the wizard confirms the migration endpoint. For example, "mail.contoso.com". Click Next.
On the Move configuration page, enter a name for the migration batch in the New migration batch name text field. Use the down arrow Down Arrow Icon to select the Target delivery domain for the mailboxes that are migrating to Office 365. In most hybrid deployments, this is the primary SMTP domain used for the Exchange Online organization mailboxes. For example, contoso.mail.onmicrosoft.com. Verify that the Move primary mailbox along with archive mailbox option is selected, and then click Next.
On the Start the batch page, select at least one recipient to receive the batch complete report. Verify that the Automatically start the batch option is selected, and then select the Automatically complete the migration batch check box. Click New.
Note
If you select Manual Complete the batch in step 8, Exchange Online will only synchronize 95% of each mailbox in that batch. Exchange Online will periodically synchronize the batch to keep each mailbox at 95% synchronization until the batch is manually completed by clicking the Complete this migration batch, at which point the remaining 5% is migrated.
Move Exchange Online mailboxes to the on-premises organization
You can use the remote move migration wizard in the EAC in Exchange Online to move existing cloud mailboxes to the on-premises Exchange organization:
In the EAC, go to Office 365 > Recipients > Migration.
Click Add Add Icon, and then select Migrate from Exchange Online.
On the Select the users page, select Select the users that you want to move and then click Next.
On the Select the users page, click Add Add Icon and then select the Exchange Online users to move to the on-premises organization, click Add and then click OK. Click Next.
On the Confirm the migration endpoint page, verify that the FQDN of your on-premises Exchange server is listed when the wizard confirms the migration endpoint. For example, "mail.contoso.com". Click Next.
On the Move configuration page, enter a name for the migration batch in the New migration batch name text field. Then enter the target delivery domain in the Target delivery domain for the mailboxes that are migrating to Office 365 field. In most hybrid deployments, this is the primary SMTP domain used for both on-premises and Exchange Online organization mailboxes. For example, contoso.com.
Choose whether to also move the archive mailbox for the selected user and enter the database name you'd like to move this mailbox to in the Target database text field. For example, Mailbox Database 123456789. Click Next.
On the Start the batch page, select at least one recipient to receive the batch complete report. Verify that Automatically start the batch is selected, and then select the Automatically complete the migration batch check box. Click New.
Step 4: Remove completed migration batches
After your mailbox moves have completed, we recommend removing the completed migration batches to minimize the likelihood of errors if the same users are moved again.
To remove a completed migration batch:
Open the EAC and navigate to Office 365 > Recipients > Migrations.
Click a completed migration batch, and then click Delete Delete icon.
On the deletion warning confirmation dialog, click Yes
I hope this manual method will be helpful!
Mark Wilson