Received file still encrypted

I'm trialling Mendelson AS2.

I've created a partner, who I can send files to without problems. However, when I receive files from the partner, the file is still encrypted.

When I created my local station, I chose the Mendelson Key 4 as inbound and outbound. I then created a certificate, using Key 4 as my alias. I then gave that certificate to the partner. Was that the correct way to set up a local station?

Thanks in advance,