update!: Add Stalwart mail server (#2936)

Signed-off-by: redoomed1 <redoomed1@privacyguides.org>
Signed-off-by: fria <fria@privacyguides.org>
Signed-off-by: Daniel Gray <dngray@privacyguides.org>

docs/email.md

@@ -249,9 +249,31 @@ Tuta doesn't offer a digital legacy feature.
 
 ## Self-Hosting Email
 
-Advanced system administrators may consider setting up their own email server. Mail servers require attention and continuous maintenance in order to keep things secure and mail delivery reliable.
+Advanced system administrators may consider setting up their own email server. Mail servers require attention and continuous maintenance in order to keep things secure and mail delivery reliable. In addition to the "all-in-one" solutions below, we've picked out a few articles that cover a more manual approach:
 
-### Combined software solutions
+- [Setting up a mail server with OpenSMTPD, Dovecot and Rspamd](https://poolp.org/posts/2019-09-14/setting-up-a-mail-server-with-opensmtpd-dovecot-and-rspamd) (2019)
+- [How To Run Your Own Mail Server](https://www.c0ffee.net/blog/mail-server-guide) (August 2017)
+
+### Stalwart
+
+<div class="admonition recommendation" markdown>
+
+![Stalwart logo](assets/img/email/stalwart.svg){ align=right }
+
+**Stalwart** is a newer mail server written in Rust which supports JMAP in addition to the standard IMAP, POP3, and SMTP. It has a wide variety of configuration options, but it also defaults to very reasonable settings (in terms of both security and features) making it easy to use immediately. It has web-based administration with TOTP 2FA support, and it allows you to enter your public PGP key to encrypt **all** incoming messages.
+
+[:octicons-home-16: Homepage](https://stalw.art){ .md-button .md-button--primary }
+[:octicons-info-16:](https://stalw.art/docs/get-started){ .card-link title="Documentation" }
+[:octicons-code-16:](https://github.com/stalwartlabs){ .card-link title="Source Code" }
+[:octicons-heart-16:](https://github.com/sponsors/stalwartlabs){ .card-link title="Contribute" }
+
+</div>
+
+Stalwart's [PGP implementation](https://stalw.art/docs/encryption/overview) is unique among our self-hosted recommendations, and allows you to operate your own mail server with zero-knowledge message storage. If you additionally configure Web Key Directory on your domain, and if you use an email client which supports PGP and Web Key Directory for outgoing mail (like Thunderbird), then this is the easiest way to get self-hosted E2EE compatibility with all [Proton Mail](#proton-mail) users.
+
+Stalwart does **not** have an integrated webmail, so you will need to use it with a [dedicated email client](email-clients.md) (or find an open-source webmail to self-host, like Nextcloud's Mail app). We use Stalwart for our own internal email at *Privacy Guides*.
+
+### Mailcow
 
 <div class="admonition recommendation" markdown>
 
@@ -266,6 +288,8 @@ Advanced system administrators may consider setting up their own email server. M
 
 </div>
 
+### Mail-in-a-Box
+
 <div class="admonition recommendation" markdown>
 
 ![Mail-in-a-Box logo](assets/img/email/mail-in-a-box.svg){ align=right }
@@ -278,11 +302,6 @@ Advanced system administrators may consider setting up their own email server. M
 
 </div>
 
-For a more manual approach we've picked out these two articles:
-
-- [Setting up a mail server with OpenSMTPD, Dovecot and Rspamd](https://poolp.org/posts/2019-09-14/setting-up-a-mail-server-with-opensmtpd-dovecot-and-rspamd) (2019)
-- [How To Run Your Own Mail Server](https://c0ffee.net/blog/mail-server-guide) (August 2017)
-
 ## Criteria
 
 **Please note we are not affiliated with any of the providers we recommend.** In addition to [our standard criteria](about/criteria.md), we have developed a clear set of requirements for any email provider wishing to be recommended, including implementing industry best practices, modern technology and more. We suggest you familiarize yourself with this list before choosing an email provider, and conduct your own research to ensure the email provider you choose is the right choice for you.

docs/tools.md

@@ -226,8 +226,9 @@ If you're looking for added **security**, you should always ensure you're connec
 
 <div class="grid cards" markdown>
 
-- ![Mailcow logo](assets/img/email/mailcow.svg){ .twemoji loading=lazy } [Mailcow](email.md#self-hosting-email)
-- ![Mail-in-a-Box logo](assets/img/email/mail-in-a-box.svg){ .twemoji loading=lazy } [Mail-in-a-Box](email.md#self-hosting-email)
+- ![Stalwart logo](assets/img/email/stalwart.svg){ .twemoji loading=lazy } [Stalwart](email.md#stalwart)
+- ![Mailcow logo](assets/img/email/mailcow.svg){ .twemoji loading=lazy } [Mailcow](email.md#mailcow)
+- ![Mail-in-a-Box logo](assets/img/email/mail-in-a-box.svg){ .twemoji loading=lazy } [Mail-in-a-Box](email.md#mail-in-a-box)
 
 </div>
 </div>

theme/assets/img/email/stalwart.svg

@@ -0,0 +1 @@
+<svg width="128" height="128" version="1.1" viewBox="0 0 33.867 33.867" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.2118 0 0 .2118 -9.7639 -9.7745)" fill="#db2d54"><path d="m130.1 56.6h-8.1l-75.9 43.8v14l75.9 43.8h8.1l75.9-43.8v-14zm55.7 50.8h-59.7v-34.5zm-59.7 34.5-59.7-34.5 45.7-26.4v34.2l10.7 6.2h38.8z"/><path d="m46.1 133.1v18.6l75.9 43.9h8.1l75.9-43.9v-18.6l-79.9 46.1z"/><path d="m194.8 195.6 11.2-6.5v-18.7l-43.5 25.2z"/><path d="m46.1 189.1 11.2 6.5h32.4l-43.6-25.2z"/></g></svg>