Created attachment 186562 [details]
error msg 1: no signature 2. no e-mail editor

Kontact
Version 6.5.1 (25.08.1)
FreeBSD 14.3-RELEASE-p5

SUMMARY
KMail fails to sign an e-mail with S/MIME, although a valid S/MIME certificate is installed

STEPS TO REPRODUCE
1. Have a S/MIME certificate installed and enable "sign e-mails" in kontact/kmail
2. Write an e-mail & send it under the identity matching the one in the certificate
3. Klick "Sign..." when asked if you want to sign the e-mail 

OBSERVED RESULT
An irritating error message dialog box stating that "the receipients signing settings contain no hint matching any of your signing keys", when canceling a 2nd strange message occurs: "No e-mail editor could be started"

EXPECTED RESULT
The e-mail should be signed.

SOFTWARE/OS VERSIONS
FreeBSD: 14.3-RELEASE-p5
Windows: 
macOS: 
(available in the Info Center app, or by running `kinfo` in a terminal window)
Linux/KDE Plasma: 
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.18.0
Qt Version: 6.9.3

ADDITIONAL INFORMATION
Note that this used to work in a previous version with my old S/MIME certificate (unfortunately it was lost on a crashed SSD).