How do I migrate my data to Proton Mail without losing my old emails?

Proton Mail lets you import your emails directly from your old account using their built-in migration tool. It's the simplest way to keep your entire history intact. You first need to create your Proton Mail account, then access the migration settings. Proton will ask you for your credentials from your old email provider (Gmail, Outlook, etc.) and it'll automatically retrieve your emails, contacts, and folders. How long it takes really depends on the volume of data - if you have thousands of emails, count on a few hours or even up to a day.

One important thing: make sure you've enabled two-factor authentication or generated an app password for your old account if you're using Gmail or another service that requires it. Proton can't access it otherwise. During the migration, your old emails will appear in Proton with their original dates, so you get everything back in chronological order. You can also do a manual export from your old email client (download as .eml or .mbox format) and then import into Proton if the automated tool gives you trouble, but that's more tedious.

After that, you can leave your old account active for a while to verify everything arrived correctly before deleting it. Emails that were sitting in spam or secondary folders can sometimes get missed, so it's good to double-check. Do you need clarification on which platform you're leaving or on a specific step?

I migrated several personal accounts and yeah, Proton's built-in tool works pretty well, but here's something people often forget: first export your emails as .mbox from your old provider (Gmail, Outlook, whatever) before you start the import on Proton. That gives you a local backup in case something goes wrong during the transfer, so you can retry the import without stress if you need to. In the meantime keep both accounts open for a few weeks to check that the folders and labels transferred properly, because sometimes it acts up a bit with custom folders.