Sending signed and encrypted mails with Gnus to outlook users fails

[Klaus Zeitler]

Hello,
when I send signed and encrypted emails with Gnus/SMime to
outlook users, outlook shows the following error:
 Your digital ID name cannot be found by the underlying security system

outlook users can read my signed emails or my encrypted ones but no
emails that are both signed and encrypted. Even more puzzling,
Thunderbird has no problems with these emails.

I'm wondering, if this is a problem with Gnus/SMime or with outlook.
Since Thunderbird is able to read the signed and encrypted emails
this looks like an outlook problem, but when I use Thunderbird
to send signed and encrypted emails they can be opened in outlook.
Apparently Gnus/SMime is doing something differently. I'm confused.

Has anybody seen something similar and is there a workaround or fix
for this problem?

Klaus