Add more information about WKD

docs/basics/email-security.md

@@ -17,6 +17,16 @@ There is another standard which is popular with business called [S/MIME](https:/
 
 Even if you use OpenPGP, it does not support [forward secrecy](https://en.wikipedia.org/wiki/Forward_secrecy), which means if either your or the recipient's private key is ever stolen, all previous messages encrypted with it will be exposed. This is why we recommend [instant messengers](../real-time-communication.md) which implement forward secrecy over email for person-to-person communications whenever possible.
 
+## What is the Web Key Directory standard?
+
+The Web Key Directory (WKD) standard allows email clients to discover the OpenPGP key for other mailboxes, even those hosted on a different provider. Email clients which support WKD will ask the recipient's server for a key based on the email address' domain name. For example, if you emailed `[email protected]`, your email client would ask `privacyguides.org` for Jonah's OpenPGP key, and if `privacyguides.org` has a key for that account, your message would be automatically encrypted.
+
+In addition to the [email clients we recommend](../email-clients.md) which support WKD, some webmail providers also support WKD. Whether *your own* key is published to WKD for others to use depends on your domain configuration. If you use an [email provider](../email.md#openpgp-compatible-services) which supports WKD, such as Proton Mail or Mailbox.org, they can publish your OpenPGP key on their domain for you.
+
+If you use your own custom domain, you will need to configure WKD separately. If you control your domain name, you can set up WKD regardless of your email provider. One easy way to do this is to use the "[WKD as a Service](https://keys.openpgp.org/about/usage#wkd-as-a-service)" feature from keys.openpgp.org, by setting a CNAME record on the `openpgpkey` subdomain of your domain pointed to `wkd.keys.openpgp.org`, then uploading your key to [keys.openpgp.org](https://keys.openpgp.org/). Alternatively, you can [self-host WKD on your own web server](https://wiki.gnupg.org/WKDHosting).
+
+If you use a shared domain from a provider which doesn't support WKD, like @gmail.com, you won't be able to share your OpenPGP key with others via this method.
+
 ### What Email Clients Support E2EE?
 
 Email providers which allow you to use standard access protocols like IMAP and SMTP can be used with any of the [email clients we recommend](../email-clients.md). Depending on the authentication method, this may lead to the decrease security if either the provider or the email client does not support OATH or a bridge application as [multi-factor authentication](multi-factor-authentication.md) is not possible with plain password authentication.
@@ -25,7 +35,7 @@ Email providers which allow you to use standard access protocols like IMAP and S
 
 A smartcard (such as a [YubiKey](https://support.yubico.com/hc/en-us/articles/360013790259-Using-Your-YubiKey-with-OpenPGP) or [Nitrokey](https://www.nitrokey.com)) works by receiving an encrypted email message from a device (phone, tablet, computer, etc.) running an email/webmail client. The message is then decrypted by the smartcard and the decrypted content is sent back to the device.
 
-It is advantageous for the decryption to occur on the smartcard so as to avoid possibly exposing your private key to a compromised device.
+It is advantageous for the decryption to occur on the smartcard to avoid possibly exposing your private key to a compromised device.
 
 ## Email Metadata Overview
 

docs/email.md

@@ -18,7 +18,7 @@ For everything else, we recommend a variety of email providers based on sustaina
 
 ## OpenPGP Compatible Services
 
-These providers natively support OpenPGP encryption/decryption and the Web Key Directory (WKD) standard, allowing for provider-agnostic E2EE emails. For example, a Proton Mail user could send an E2EE message to a Mailbox.org user, or you could receive OpenPGP-encrypted notifications from internet services which support it.
+These providers natively support OpenPGP encryption/decryption and the [Web Key Directory standard](basics/email-security.md#what-is-the-web-key-directory-standard), allowing for provider-agnostic E2EE emails. For example, a Proton Mail user could send an E2EE message to a Mailbox.org user, or you could receive OpenPGP-encrypted notifications from internet services which support it.
 
 <div class="grid cards" markdown>
 
@@ -85,7 +85,7 @@ Certain information stored in [Proton Contacts](https://proton.me/support/proton
 
 Proton Mail has [integrated OpenPGP encryption](https://proton.me/support/how-to-use-pgp) in their webmail. Emails to other Proton Mail accounts are encrypted automatically, and encryption to non-Proton Mail addresses with an OpenPGP key can be enabled easily in your account settings. They also allow you to [encrypt messages to non-Proton Mail addresses](https://proton.me/support/password-protected-emails) without the need for them to sign up for a Proton Mail account or use software like OpenPGP.
 
-Proton Mail also supports the discovery of public keys via HTTP from their [Web Key Directory (WKD)](https://wiki.gnupg.org/WKD). This allows people who don't use Proton Mail to find the OpenPGP keys of Proton Mail accounts easily, for cross-provider E2EE.
+Proton Mail also supports the discovery of public keys via HTTP from their [Web Key Directory (WKD)](https://wiki.gnupg.org/WKD). This allows people who don't use Proton Mail to find the OpenPGP keys of Proton Mail accounts easily, for cross-provider E2EE. This only applies to email addresses ending in one of Proton's own domains, like @proton.me. If you use a custom domain, you must [configure WKD](./basics/email-security.md#what-is-the-web-key-directory-standard) separately.
 
 #### :material-information-outline:{ .pg-blue } Account Termination
 
@@ -135,7 +135,7 @@ However, [Open-Exchange](https://en.wikipedia.org/wiki/Open-Xchange), the softwa
 
 Mailbox.org has [integrated encryption](https://kb.mailbox.org/display/MBOKBEN/Send+encrypted+e-mails+with+Guard) in their webmail, which simplifies sending messages to people with public OpenPGP keys. They also allow [remote recipients to decrypt an email](https://kb.mailbox.org/display/MBOKBEN/My+recipient+does+not+use+PGP) on Mailbox.org's servers. This feature is useful when the remote recipient does not have OpenPGP and cannot decrypt a copy of the email in their own mailbox.
 
-Mailbox.org also supports the discovery of public keys via HTTP from their [Web Key Directory (WKD)](https://wiki.gnupg.org/WKD). This allows people outside of Mailbox.org to find the OpenPGP keys of Mailbox.org accounts easily, for cross-provider E2EE.
+Mailbox.org also supports the discovery of public keys via HTTP from their [Web Key Directory (WKD)](https://wiki.gnupg.org/WKD). This allows people outside of Mailbox.org to find the OpenPGP keys of Mailbox.org accounts easily, for cross-provider E2EE. This only applies to email addresses ending in one of Mailbox.org's own domains, like @mailbox.org. If you use a custom domain, you must [configure WKD](./basics/email-security.md#what-is-the-web-key-directory-standard) separately.
 
 #### :material-information-outline:{ .pg-blue } Account Termination