[Users] Encrypting all outgoing Mails in Sentfolder

[claws at plaintext.ath.cx]

Sorry, this question has maybe been asked already, but I still could
find the right solution.
The question is. How can I teach CM to encrypt (with my key) every
outgoing mail automatically and store it in the "Sent"-Folder.

I could come up with some MTA, procmail, BCC-filter method, but that is
weard. 
It should be a small step for CM and a big one for the CM users :-)

At the moment every mail in my inbox is encrypted apart from the
sent-Folder (with makes the whole business useless somehow.)

Is there a simple solution?

Thanks in advance
t.