send encrypted message to external recipient with outlook 2003

Hello to all of you

At the company where I work, a client requested that all e-mail coomunicaiton between them and us should be encrypted. They specify that that they use PGP 8.1 (www.pgp.com)

Tell me if I’m wrong.

If I understand correctly. I have to use the same program to be able to send encrypted messages to them and read their encrypted messages.

If they use PGP 8.1 and we decide to use for example CGeep, it will not work

Just sending the public key to the other party is not enough.

Thank you in advance for your help

Michel