How to migrate Hosted Exchange to Office 365 manually?

The cutover migration is as simple as getting all users from the source server and pasting them in Office 365. Sounds simple, but there is much more to that. In another article, you can find a detailed cutover migration plan. Below, you can find some steps you need to take before you migrate mailboxes from Exchange to Office 365.

First, you need to prepare your environment. The preparation and planning might take less time than the actual migration, but it still requires a lot of attention. Below, you can find a short task list for a cutover migration.

Update your Exchange 2010 server to SP3. While it is not mandatory, it is highly recommended.
Before you perform the cutover migration, you should disable directory synchronization and unified messaging, if they are turned on.
Enable and configure Outlook Anywhere. In the newest Exchange Server flavors, this is done by default. In Exchange 2010; however, you need to complete this step on your own. To successfully configure Outlook Anywhere, you need to install a trusted SSL certificate and the RPC over HTTP component on your server. You can test whether the configuration went well by connecting to your Exchange 2010 from outside of your network. This will be tested automatically when you connect Office 365 to Exchange 2010, but the manual test will save you some possible hassle later.
Assign permissions. There are certain permissions you must assign to the account used for migration. It is common practice to use a dedicated user account for the migration, which has only the minimal required permissions assigned. The permissions the migrating account needs are Application Impersonation and View-Only Configuration for the Exchange Server and Office 365. Additionally, the target Office 365 environment requires View-Only Recipients role and User management administrator if it is also responsible for re-creating users in Exchange Online.
Create a mail-enabled security group in Office 365. Otherwise, the migration service cannot provision any migrated groups as security groups in Office 365
Verify your domain in Office 365. It requires you to add a TXT record in your DNS zone.
Use Exchange Admin Center to create a migration endpoint. The endpoint contains all the information necessary to connect your Exchange 2010 server to Office 365.
Create and start the cutover migration batch. The batch includes all mailboxes and requires the migration endpoint configured a step before. This is the point when the actual migration happens. After the data transfer is finished, it is worth verifying if everything had gone well. You also need to assign licenses to users.
Now for the post-migration cleanup, switch your domain’s MX record to point to Office 365. After the TTL passes, emails are routed directly to Office 365. You can delete your migration batch and decommission the on-premises servers.

I hope this method will be useful!
Paul Wilson