Without a good importing tool (warning: the GSuite importing tools are shit), I recommend "imapsync": https://github.com/imapsync/imapsync https://github.com/i

Without a good importing tool (warning: the GSuite importing tools are shit), I recommend "imapsync": https://github.com/imapsync/imapsync https://github.com/imapsync/imapsync After cloning the repository and installing the listed dependencies (some Perl packages available in your Brew / Ubuntu repository already), you can do: imapsync \ --host1 imap.old.com \ --user1 "old@email.com" \ --password1 xxxxxxxxxxxxx \ --ssl1 \ --host2 imap.new.com \ --user2 "new@email.com" \ --password2 yyyyyyyyyyyyy \ --ssl2 \ --errorsmax 1000000 \ --syncinternaldates \ --useheader 'Message-Id' \ --noreleasecheck \ --noexpunge \ --automap Works great for importing to and from Gmail, but you might want to add a folder rewrite for the Sent folder (with --f1f2). But with FastMail, for those interested, the out of the box importing tools in their web interface work great, so no need for any command line tools.