How to enforce S/MIME encryption in Apple Mail

We've set up Apple Mail on our Macs with S/MIME encryption which works quite well. However, users are able to select or deselect encryption by clicking on the lock symbol when writing an email. Sometimes users deselect encryption for some reason (maybe just accidentally), then Mail keeps that setting for any subsequent emails. Is there a way to configure Apple Mail in a way that it enforces encryption if a certificate is available for the recipient, so it cannot be turned off by the user? Maybe through a profile?