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Email migration involves transferring mail from one system to another. Before starting a migration, the limits and procedures are reviewed to ensure that the expected performance and behavior will be accomplished after the migration.
Microsoft Exchange Online provides all the benefits of a cloud-based email service with the robust implementation capabilities of an on-premises Exchange server.
Migration cases

Exchange local
Exchange Server Accounts (v. 2003, 2007, 2010). This scenario allows you to migrate all email, calendar, and contacts from users’ mailboxes to Office 365. This migration can be total, in batches, or hybrid.

Google / Gmail
Accounts in Gmail/Google Apps (G Suite). This is a migration using the IMAP protocol, which only migrates items in the inbox. Contacts and calendars can be migrated by users or through third-party tools.
Hosting internet (POP/IMAP)
Accounts hosted by a third-party provider. This migration is done by exporting/importing the .pst files.
