Exchange Online Migration

Exchange On-Premises to Exchange Online Migration
  1. Cutover migration
  2. Staged migration
  3. Hybrid migration
  4. Minimal Hybrid
Exchange Online to Exchange Online Migration (Tenant to Tenant)
  1. PST Migration
  2. 3rd Party Tool
Other Email Services to Exchange Online Migration
  1. IMAP migration
  2. Gsuite to Office 365 Migration (inbuilt Tool)
  3. 3rd Party Tool
  4. PST migration

Exchange On-Premises to Exchange Online Migration

Cutover Migration
This migration type is suitable for the below scenario.
Prepare
Migrate
Reference
https://docs.microsoft.com/en-us/exchange/mailbox-migration/mailbox-migration
Staged Migration
This migration type is suitable for the below scenario.
Prepare
Migrate
Reference
https://docs.microsoft.com/en-us/exchange/mailbox-migration/perform-a-staged-migration/perform-a-staged-migration
Hybrid Migration
This migration type is suitable for the below scenario.
Use this type of migration to maintain both on-premises and online mailboxes for your organization and to gradually migrate users and email to Office 365. Use this type of migration if,
Option 1 - Exchange 2010
Prepare
Migrate
Option 2 - Exchange 2013
Prepare
Migrate
Option 3 - Exchange 2016
Prepare
Migrate
Minimal Hybrid
Prepare
Use minimal hybrid to migrate emails if you:
Migrate

Exchange Online to Exchange Online Migration (Tenant to Tenant)

Office 365 does’t support or provide any tool for Tenant to Tenant migration. This can be done through 2 Methods.
  1. PST Migration
  2. 3rd Party Tool.
PST Migration
Network Import can be used to upload the data to Azure Storage & then map it to Office 365 Mailbox.
Ship Drives option allows customers to copy their data to hard drive and ship the drive to the Microsoft physical location. The data import will be performed at back end.
PST migration is recommended for the Office 365 tenant with Exchange Online (EXO) Services alone. Incase of a tenant with SharePoint Online (SPO) or OneDrive for Business (ODB) , then it is advisable to use the 3rd party tool as it gives option to migrate all Office 365 Data (EXO, SPO & ODB) in single console. There is no inbuilt tool provided by Microsoft to migrate SPO & ODB data.
3rd Party Tool
One of the best migration tool for this scenario is Migration Wiz by Bittitan.
Migration Guide for the same is available here.

Other Email Services to Exchange Online Migration

IMAP Migration
You can use the Internet Message Access Protocol (IMAP) to migrate user emails from Gmail, Yahoo, Outlook.com, and other email systems that support IMAP protocol. When you migrate the user's email by using IMAP migration, only the items in the users' inbox or other mail folders are migrated. Contacts, calendar items, and tasks can't be migrated with IMAP, but they can be by a user.
Prepare
Migrate
Note
It is advisable to migrate all mailboxes in single batch and perform the Email routing once all the mailboxes are migrated.
Also, clearing migration batches should be performed after 48 Hours of Email routing changes, to avoid any data loss.
G suite to Office 365 Migration (inbuilt Tool)
Recently, Microsoft & Google have provisioned a new migration method to migrate data from G Suite to Office 365. This migration method overcomes the drawback of IMAP migration which is a manual import of Calendar & Contacts. Also, it provides an option to migrate the data in batches and allow the migrated users to start using the Office 365 services while their pal’s mailboxes are being migrated.
Prepare
Migrate
Third-Party Tool & PST migration details remain the same as explained in Exchange Online to Exchange Online Migration (Tenant to Tenant).