K-9 Android app does not show email is signed

Checklist

• I have used the search function to see if someone else has already submitted the same bug report.
• I will describe the problem with as much detail as possible.

App

K-9 Mail

App version

23.0

Where did you get the app from?

F-Droid

Android version

12

Device model

not relevant

Steps to reproduce

1. Send an email signed with a SMIME certificate to your mailbox
2. Look at that email using K-9

Expected behavior

K-9 should show me whether the email is signed or not, and also whether the signature/certificate is valid.
Ideally, this should be some clearly visible icon which can be tapped on to get more information about the signature/certificate.

Actual behavior

K-9 does not show anything. I cannot see any difference between a signed and an unsigned email.
Not in the inbox list view, nor in the email detail view.

IMHO this is a major security issue as it facilitates email spoofing.

Logs

No response

Start by reproducing the issue with an S/MIME-signed email in K-9 Mail on Android, then compare the inbox list and email detail views for signed and unsigned messages. Done means the app visibly indicates whether a message is signed and whether its signature or certificate is valid, with access to more information.