Backup Your Email Archive

[This part 4 of a multi-part series – start here.]

Now that we’ve painstakingly archived our online email history, it’s time to carefully protect it before we delete the online copies.

Locating Your Profile Folder

Assuming you used Thunderbird, it’s pretty easy to back up all of your emails (and contacts and anything else you imported), but it’s important that you do so. For any digital data that I find important and that I can’t easily recreate somehow, I use the 3-2-1 backup rule. The TL;DR version is that in addition to the primary copy, you should have a local backup (at home, not necessarily on your computer) and offsite (in case of fire, flood, etc.). I’ll let you read the article to get more ideas on where to store your backups. But for now, let’s talk about where to find your email data and how to compress it into a single file.

If you have a ton of old emails like I do, you’re going to have to find your Thunderbird profile folder. Luckily, it’s easy to do. If you go to the Tools menu and select the “Export…” option, a window will appear with a nice “Export” button… but it also has a note that says “If your current profile is larger than 2GB, we suggest you back it up by yourself.” Unfortunately, the app apparently isn’t smart enough to determine this for you. But click the “Open profile folder” link which will open a file viewer (Finder or File Explorer) showing you your profile folders, pre-selecting the one you’re currently using.

You should be able to see the size of the profile folder (if not, here’s how: Windows / macOS). Unless you explicitly created separate profiles, all your emails – for all your email accounts – should be in this one folder. Now you just need to make a copy of this folder and put it somewhere safe. We’ll compress (“zip”) it to save space and turn the folder into a single (large) file.

Zipping Up Your Archive

If your profile is relatively small, you can simply click the Export button and let Thunderbird create the ZIP file for you. However, Thunderbird recommends manually backing up profiles larger than 2GB. So assuming you have more than 2GB, you just want to make a compressed copy of this entire profile folder.

You have a choice to make first. If you want to store this zipped archive somewhere that other people may have access to or if you just want to be super secure, then you’ll want to protect this archive with a password using top-notch encryption. But if you’re going to store it on a computer that’s already private and secure, then you can skip the password.

If you want to add a password, I have a whole article on how to do this, including pictures, here. You’ll need to download a cheap app for macOS called Keka or use the free 7zip for Windows.

If you don’t need a password, you can use the built-in zip/compress functions in your operating system:

• macOS: Right-click the profile folder and select “Compress <folder name>”.
• Windows: Right-click the profile folder and select “Show more options”, then “Send to”, then “Compressed (zipped) folder”.

In both cases, this will create a ZIP file with the same name as the folder. This may take a long time, depending on the speed of your computer, the amount of RAM your computer has, and the size of the profile folder. I would personally change the name to something like “email-archive-2026-06-14.zip”, so you know what it is and when you made it.

Congratulations!! You now have a full copy of all your historical emails in Thunderbird, which is easy to search and read, including attachments. And you also have a backup of all those emails, which you can re-import to Thunderbird or most email apps. If you followed my recommendation to use Maildir storage, you’ll find your messages as individual .eml files under the ImapMail folder in the archive. These files can be opened directly or imported into many other email programs. You can also restore the entire Thunderbird profile or use the ImportExportTools NG plugin.

Deleting Your Online Emails

Let me start by saying this step is completely optional. Also, you don’t have to do this right away. But the premise we started with in the first article was that we want to minimize the emails we have stored in the cloud with our original email providers. As long as that data exists, it can be mined for information – not just about you, but everyone you emailed with. It can also be leaked, stolen or abused. In this new age of AI, online data is more vulnerable than ever, creating powerful incentives to collect, analyze, and monetize it.

Before I tell you how to do this, I want to note a few very important things:

• I would not delete your emails from your online mail provider (Gmail, Outlook, Yahoo Mail) until you’re absolutely certain you have a full backup on your machine. See the previous article for help verifying your archive.
• Make sure you can actually open the ZIP file you created and browse its contents.
• I would not close your email account. Many email providers will eventually recycle email addresses – that is, allow someone else to claim your address. That could cause a lot of confusion and even open your contacts to potential scams.

Once you’re sure you no longer need online copies of your emails, here are the instructions for deleting your old emails:

• Gmail (Google)
• Yahoo Mail
• Outlook (Microsoft)

BONUS: Another Email Archive Tool

This tool was brought to my attention by a reader, and it looks very promising – but it’s a little trickier to set up. It’s a free and open source project called Bichon. It runs using a container technology called Docker, which you can run on Windows and macOS (as well as Linux), but you would have to install a framework that supports running Docker containers. There’s Docker Desktop, obviously, but that framework often requires admin/root privileges, which has led to vulnerabilities in the past. If I were experimenting with it, I’d probably look at Docker in rootless mode or (most likely) try using Podman instead.

I haven’t tried this myself yet, but I plan to try it. If I find anything interesting, I’ll update this article.