Encryption Certificates

[Jaime Castells]

I am having trouble sending encrypted email to a recipient
from whom I have recieved a certificate. First I found
that encryption options would not turn on unless I also
had a certificate, but then I got a certificate form
www.thawte.com and now I get an error when I try to send
encrypted email saying that the recipient will not be able
to read the encrypted message. He has a Verisign
certificate.

Is there an interoperability problem between certificate
authorities?

Also, why does Outlook reaquire a certificate before it
can send encrypted messages? With other email clients, I
can encrypt a reply to a sender who has provided their
public key without having a certificate of my own.

TIA!