So, I've received an S/MIME-encrypted email and I'd like to answer with an encrypted email. The first issue was that their address was, for whatever reason, not automatically added to my address book. But now, after manually adding them, TB still complains about some certificate issue it doesn't further explain. In the account settings under "Manage S/MIME certificates", their S/MIME certificate isn't listed, so most likely that's teh issue. Right clicking the contact's address in the mail I received only shows an option to discover their OpenPGP key, which can't be found (as they'll only have the S/MIME vertificate). Now, how do I tell Thunderbird to add their S/MIME certificate to the certificate storage so I can answer with an S/MIME encrypted email? Firefox 128 Flatpak on Debian 13.