WebClient supports personal SSL certificates. It allows you to send and receive digitally signed messages.
At first, you need to supply your certificate to your account. WebClient will then use your certificate to sign.
1. Get a certificate
You can purchase a certificate online or get it for free at Actalis, for example.
2. Add a certificate to the WebClient
Navigate to Settings through your Avatar (top right corner) icon and hit the "Upload" button.
Upload the certificate by entering the passphrase you have received during the registration of your certificate.
Once you've added the certificate successfully, you should identify its validity when you double-click on it.
3. Send a digitally signed message
You can tell the WebClient to sign all messages by default via Settings:
Or you can do it on-demand.