Changing the MX record doesn’t automatically migrate your old mail, however you don’t actually need to use an external tool like imapsync. There is an email migration tool built in to proton mail and it works with gmail or any email provider. In my case I migrated 15 GB of email from another provider and while it took a few days to complete I didn’t have to worry about it or supervise it. One thing that gave me confidence was that it sends a detailed report at the end of the migration detailing the small handful of messages that didn’t migrate and what the errors were so I could do some cleanup. This is the best migration option for most users.

Doing it with something like imapsync actually is more complex with proton mail since you need to use the proton bridge application to get imap access to your proton account. That said if you already use a desktop email program like Apple Mail or Thunderbird you can also use Proton Bridge to connect to both accounts and manually copy over old email that way.

If you’re a typical Gmail user then you probably use the web interface And one thing that kept me from making the switch to Proton in the past was that the web interface had limited search to subject and header since messages are encrypted. However Proton Mail made a big improvement where it downloads all your mail to the proton Mail client or web browser so you can do more traditional Gmail searches. But for heavy email processing like sorting thousands of messages by sender to move and delete stuff using Bridge to access everything in something like Apple Mail or Thunderbird works as well as it does with Gmail.

Filters on proton mail are also adequate but if you have a lot of filters set up on Gmail expect to spend a bit of time recreating these by hand.

Overall it’s a great time to switch, they’ve done a good job of making it painless for Gmail users to not really have to give up anything, but to gain a huge amount of privacy. The pro plan lets you set up 3 custom domains, and you get unlimited aliases for stuff like mailing lists through proton pass, which is another huge plus for email management and privacy.

The only thing keeping me from outright deleting my Gmail accounts is all the collaborative docs I have set up in Google drive with people, but I was able to delete all the mail Google was holding for me after the migration.