(USING GOOGLE MIGRATION EWS ONLINE IMPORT TOOL)
Source: https://support.google.com/a/answer/6003165?hl=en
1.) Open Exchange Management Shell
2.) New-ManagementRoleAssignment –Name:impersonationAssignmentName –Role:ApplicationImpersonation –User:administrator
3.) Get-WebServicesVirtualDirectory|fl
4.) Copy EWS Eternal URL
5.) Go to admin.google.com
6.) Migrations
7.) Choose Exchange 2010 using Exchange EWS
8.) Paste EWS External URL from step 4
9.) Next
10.) Make sure the users "default SMTP email address" for "Exchange Email" field is listed.
11.) Start Import