[imp] S/MIME Encryption

[mail@janboysen.de]

Hi all.
First of all I use imp-h3-4.0.3 with horde-3.0.4. When I try to send an
encryped message IMP generated an error message telling me that I need MY
public key for that. This confuses me a little bit since I think it is
only necessary to have the public key from the person I want to send an
encryped message. Is it not possible to send encrypted messages without
having a own public key or do I something wrong?
Thanks for your help 
Jan