A feature where one could generate, or manually add, a OpenPGP key to a webmail account and enable automatic signing of outgoing E-Mails. Stalwart would then, whenever a request is made to send an E-Mail to somewhere, sign it with the key before sending it out.
Currently there is no way to automatically sign E-Mails generated by a self hosted service connected to the Mailserver, such as a self hosted Forgejo instance. This would allow a user to generate a key for their E-Mail and have those E-Mails then signed when they are sent to validate to users that the E-Mails are authentic and didn’t come from a third party.
A nice to have would also be a one-click ability to upload the Key to something like keys.openpgp.org so that it can be easily discovered by users if they manually look or use a app like Thunderbird which automatically should discover the key of that address.