Impersonate user Office 365 account is a most important thing.
1. The application impersonation role in Office 365 has many benefits, the following are few common reasons for setting up impersonation in Office 365:
2. Reduces the effect of throttling and connection limits.
3. Allows to migrate multiple mailboxes concurrently.
4. Eliminates “Connection did not succeed” errors.
5. Uses an O365 admin account without assigning any license to it.