"Unknown Error" with s/mime wildcard

[TheCuteFoxxy]

Describe the bug
"Unknown Error" when signing mail using a wildcard s/mime.

To Reproduce
Steps to reproduce the behavior:

1. Generate a "wildcard" s/mime cert and key with OpenSSL
2. Import the cert and key into Snappymail
3. Compose new email
4. Ensure "sign" option is selected and available
5. Observe unknown error when sending

Expected behavior
The email should send and be signed using the wildcard cert

Screenshots

Please complete the following information:

• Browser: Firefox 125.0.3
• IMAP daemon: dovecot
• PHP version: 8.1.27
• SnappyMail Version: 2.36.1
• Mode: Nextcloud

Debug/logging information

• Log File

Additional context
None

[the-djmaze]

The goal of S/MIME is to prove who sent the e-mail (signature) and encrypt the e-mail between the sender and recipient (providing the confidentiality).

So currently there is no wildcard support as it does not make any sense.

[TheCuteFoxxy]

Unless I missed it somewhere, Snappymail doesn't automatically send the public keys along with encrypted or signed mails. So without the user physically providing every single person the key, then signatures can't be verified and encryption can't be decrypted.

If 5 people need to verify their emails between each other, than each person has to give the other 4 people the public key manually.

A wildcard prevents this problem when its being used across the same domain since everyone has the same keys for that domain, but other domains (such as gmail) doesn't, which is fine.

[the-djmaze]

Attaching your public key is a better option, like you ask in #1587