S/MIME Email Signing

This plugin is for signing all outbound emails with an S/MIME certificate.

It uses phpmailer to automatically sign emails. Here are the prerequisites to use this plugin:
* This plugin is for single-user WordPress site, such as a personal blog. I don’t know what will happen if you put it in a multi-user site.
* PHP 8.3 and above are recommended. Make sure your PHP has openssl extension, which is usually installed by default.
* You should use another plugin, such as FluentSMTP, to send emails through an external SMTP server.