KMail does not always show attachments of as signed and encrypted mail.
I prefer "show only in headers".
But in some mails attachments are not shown in the header.
Here is what I see in KMail (with attachments "in headers only" and with expert plugin) and in Akonadi Console:
When I enable "Show attachments as Icons", those are displayed "at the bottom" in this mail.
But not in the following example in HTML:
just so you believe me about the view setting:
But none of the settings there makes any difference.
The same mail in Akonadi Console: