Hello,

I am sorry to report that Protonmail Free does not work with Thunderbird, or any email client for that matter. They restrict their external mailservers to paid users only.

It shouldn't be impossible to do without their webmail client with some sneakily made requests, but that I am aware, there is not a way out there.

I am pretty sure that free stuff is usually worth what one pays for it, so am willing to pay for a good service. I would really appreciate some information on how Proton and Thunderbird get along now.

Completely sorry to assume that you wouldn't pay for the service.

Protonmail has an interesting service they call bridge. Protonmail bridge makes a local mailserver that accepts email and encrypts it their way before it is sent through the internet. Note that because it uses a local mailserver, Thunderbird will complain that the certificate is invalid.

I personally can't confirm that it works perfectly, as I use a different mail service; however, the fact that Protonmail has a guide for it means that it should work pretty well.

I will send the links as a separate message because links need to be approved by a moderator

Installation instructions link Thunderbird setup link

I do not doubt that you could also configure a firewall to allow other of your devices to connect to one collective mailserver over an intranet as well

I very recently became a paid ProtonMail user and I have found the interface between ProtonMail and Thunderbird works very well. The only problem I have run into is ProtonMail puts all incoming mail into the Inbox on their server by default. Even though you can create sub folders and filters on the ProtonMail platform you are not allowed to do the same within your Thunderbird account for the ProtonMail (username@protonmail.com) for some reason. I'm not sure I follow their logic but I can see where you might be defeating the purpose of having encrypted mail if you are going to scatter the incoming mail to the winds. However all the mail that is in the Thunderbird Inbox is decrypted. Perhaps someone with a deeper understanding of how email programs function can provide some insight. I was able to overcome this problem for my online shopping emails by creating a separate offline account in Thunderbird that I named Local Folders. I then created a filter to move the shopping emails from the ProtonMail Inbox to the Local Folders > Amazon, Insurance, etc. folders and it works great.

Good to see that you found something that works.

Yes, these messages will be decrypted, and this is because the "connector" is effectively the web client decrypting and then fowarding them to Thunderbird.

I've been using a (paid) Protonmail account with Thunderbird for a couple of years now. At some point last year, after an update to their bridge software, the automatic filtering I had set up for my Protonmail Inbox quit working, and mail messages would just accumulated in it until I run the filters associated with the account manually. As a partial workaround I installed an TB addon named New Folder Filters Button that lets me run the filters by clicking on a Toolbar icon (after first selecting the Inbox folder).

I filed a bug report with Protonmail, then quite a while later, they closed the bug report because they could not reproduce the problem — so it's never been fixed.

Other than that, I have not had any major issues using it with TB, including any related to the creation of sub-folders or that sort of thing. It seems like retrieving message through their Bridge software is a bit slow, but it's tolerable.

However, because of the auto Inbox filtering issue, I cannot recommend them as a provider for TB, unless security is extremely important to you. I'm going to switch someday, but the thought of changing all my mail email address has prevented me from doing it so far — it's a really pain to have to do as I've learned from previous experience.