gmail smime, sends two messages one is not encrypted. Experience?

[Uwe Brauer]

Hi

This might be slightly off topic, but I would really appreciate some
feedback.

My university uses a special gmail service for academic institutions.
Recently gmail provides smime support itself and this has been enabled
by my university.

Now comes the strange thing:
I use smime mostly with emacs+gnus, sometimes with thunderbird.

When I sent (with emacs or thunderbird) an encrypted+signed message [1], to a person in my
university which whom I have interchanged the public key, since some
time, *two* messages are sent, one 

    1. Is encrypted and signed

    2. The other is only signed.

Can somebody please confirm this strange behavior? 

Is this connected to the fact that my university enabled smime support?


It seems to me a complete security breach.

Regards

Uwe Brauer 

Footnotes:
[1]  purely encrypted messages are rejected by the server