“feature request”?

This plugin encrypts *all* outgoing email from WordPress to any recipient with a public key in their user profile, so your question indicates either a bug in this plugin (unlikely if it’s still working for you when you receive emails), that the other plugins you mentioned do not use WordPress’s built-in wp_mail features (also unlikely, but more possible and easily discoverable by checking the other plugin’s documentation and/or source code), or I don’t understand the question (highly likely).

Are you asking if emails you receive from others can be decrypted by the plugin? (The answer is no; use an email client instead.)

I still don’t understand what you are trying to do. Emails sent from your WP-powered ticketing system should *already* be encryptable; you will receive encrypted emails. So should your users, as long as they supply WordPress with their PGP public key in their WordPress profile. Since it’s a Web-based ticket system, using HTTPS will mean no machine in the middle will eavesdrop on tickets being added to the system.

You sound like you want people to be able to submit tickets via email, and encrypt those *incoming* emails, too, then decrypt those emails when they are received by the ticketing system *in WordPress*. That’s, bluntly, a bad design idea and not one I will implement. Use an email client. Use HTTPS in the browser. This already exists. No new features need to be added to do this.

Ah, I understand now. But no, I won’t do that. Your request requires the server to maintain a private key part, which is a high-value target. It changes the security implications of the plugin’s use case dramatically and isn’t something I feel comfortable to or interested in developing or maintaining. It’s also by design less secure for most use cases I can imagine, and alternatives already exist for the other use cases. It’s not something I will do myself or merge into this plugin. Sorry.