Using Thunderbird to Move Email to a New Account

You’re moving to a new email provider. Both the old and new ones have cloud-based storage. And you want to move your old mail archives to the new site, or to your local desktop/laptop.

Good: Thunderbird is able to move messages from one IMAP account to another! Just connect it to both accounts, then drag and drop! Or cut and paste if you prefer!

Gmail makes it complicated

Bad: Gmail is a bit weird in how it appears through IMAP. Every label appears as a folder. And when you move a message, it only moves it out of that folder. It’s still on Gmail under the other folders. So if you’re moving mail folder by folder, you can easily end up moving the same message repeatedly and getting multiple copies.

Worse: That includes “Important.” And “Starred.” and “All Mail.” If you move something out of the only folder it’s in, well, it’s still there in All Mail. And if you move something out of All Mail that has any other labels, Gmail will keep a copy and re-add it to All Mail.

Less Bad: Deleting a Gmail message through IMAP seems to work as you’d expect it to. Probably because it’s deleting it by message ID instead of moving it by folder.

Best ways to deal with this? Either

• Move everything at once and don’t look back, or
• Delete messages you don’t want to keep first, then remove the labels before you try to move messages over.

Tedious. But doable.

Cleaning Up

The Remove Duplicate Messages add-on for Thunderbird has worked well so far. I’ve been running it on the new account’s folders after I move a batch of messages over from Gmail.