Importing your mbox file into ProtonMail on Linux

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ProtonMail is great, but unfortunately as of the time of writing this they do not have a native Linux importer. If you're using gmail or any provider that you can get an mbox file from, you can get around it with a couple free, open source tools, but in order to use the ProtonMail Bridge you'll at least need to have a paid account with them.

Add ProtonMail to Thunderbird

First, lets add your ProtonMail account to Thunderbird:

  • Install and configure ProtonMail Bridge
  • Install Mozilla Thunderbird and add your ProtonMail account, being sure to add the bridge's username and password rather than your actual account username and password.
  • Add your account to Thunderbird following the instructions in the Bridge documentation. Note there are a couple unexpected messages that pop up, but this is normal.
  • At this point, you should see your ProtonMail messages in Thunderbird.

Add your mbox as a Local Folder

Get your mbox file from Google Takeout (if using gmail), or from whatever provider you use. Now, let's mount the mbox as a Local Folder:

  • Install the ImportExportTools Add-On to Thunderbird.
  • Right click on Local Folders in Thunderbird, choose ImportExportTools NG, then Import mbox file.
  • After the import is done, you'll have a new local folder. One thing you might notice is that your gmail chats are there. They contain a header X-Gmail-Labels: Chat you can use to filter them out, but in my case I wanted to bring them over.
  • To bring them into ProtonMail, simply select all the messages (ctrl-A) and either drag them all to the ProtonMail inbox, or right click, move, and select the ProtonMail inbox. Depending on how many messages you have, this can take a long time. For me, I had to restart Thunderbird before it would do this operation, but once I did there was a progress bar at the bottom showing which email it was copying. Depending on how many emails you have you may want to break this into multiple operations.

All done

At this point all your emails are on ProtonMail, and you no longer need Thunderbird or the ProtonMail Bridge on your computer unless you want them.

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