Thunderbird Android S/MIME encryption

Vlekjes — Mon, 18 May 2026 09:50:51 GMT

I posted an idea for adding S/MIME encryption to Thunderbird Android. Adding encryption and signing will allow organizations and individuals to use email for exchange of confidential or private information. Thunderbird Android now supports OpenPGP, but S/MIME seems to be more of an industry standard. Most mail clients support S/MIME, most are made by American big tech companies. In Europe, there is a tendency to want to move away from American big tech.

I have been using K9 as the mail program on my Android phone for a long time. Now K9 is Thunderbird, it is part of a bigger familiy and will get better support. I use Mozilla Thunderbird on my computer.

Our company, Ciphermail, makes email encryption server softeware, supporting S/MIME and PGP. A community version is available at https://gitlab.com/ciphermail/ciphermail-community-gateway/-/tree/main

We do have an android email app that is very limited in functions. Instead of continuing that app, we want to convert it to a companion app to Thunderbird Android. This would work in the same way as the OpenPGP plugin, with a separate companion app. We have created the companion app, and we'd like to submit a pull request for the code we made for the S/MIME plugin. The Ciphermail app will be open source and free.

We plan a service for our server product that would also work for the app: a certificate exchange, with which you can retrieve a certificate, if it exists, for a given email address. This will be a federated service.

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Thunderbird Android S/MIME encryption