Encryption problems

When someone sends a message and I already have their certificate, I cannot decrypt the message. It asks for a password (why???) when the sender sends the password, it still doesn’t decrypt the message. When I try to send an encrypted email I am asked for a password, but NOTHING I enter is accepted, so I cannot send an encrypted email. The implementation seems to be all wrong in eM Client. Having worked on PKI for a large organisation, I know that it should not be this complicated. Once two parties have exchanged certificates there should be seemless communication. So, what is going on here? Also the described ‘Security Profile’ dialogue is nowhere to be found. I am disappointed as eM Client has been going long enough now for these sorts of issues not to occur. Any thoughts anyone?