Solved! Go to Solution.
It does not work in the preview, but works in the actual email message. I just sent one today. The text I entered was something like this:
Download the PowerPoint file, go to https://www/xxxx.com/web_page.html
You don't need to encode it, just insert the full web address. If the receiver's email app can read html messages (most people can), then it shows up as a clickable web link.
This is already supported on our new platform which your account is on (I checked). You can copy and paste links to webpages in your follow up Email and they will be live clickable links for your attendees, unless their Email client prevents it for security.