S/MIME certs recognised as attachments

emClient, Windows version, doesn’t recognise emails with S/MIME attachments correctly.
The problem exists in emClient 10.4.5326 (97a2e75) but it lasts for some time now, actually.

emClient recognises such emails as having attachments initially (when unread) but it changes its mind once such an email is opened.
That leads to side effects. I have two search folders defined, one for emails with attachments, another for emails without attachments. Both are configured with no preview, just a list of emails.
Here’s what happens when I try and open unread email with S/MIME cert attachment from “with attachments” search folder:

  • A new window pops-up (as configured, expected behaviour) but it closes before showing a message body.
  • The message is marked as read.
  • The message is no longer listed in “with attachments” search folder.
  • The message is listed in “without attachments” search folder now.

It seems to be a consequence of wrong initial classification made by emClient initially.
emClient corrects that after opening an email, changes it classification, updates search folders in the background and closes the message as no longer matching the folder search criteria. All that in a blink of eye.