Send Mail can only send plain text. To use HTML formatting, you'll need to investigate email plug ins for FileMaker. There are a number of them that you can web search out and examine to see which best meets your needs.
Instead of the send mail, use the Open URL command. make sure to use "mailto:[emailaddress]" this will open a new email message in HTML using your default email application. google "mailto:" and you will se a bunch of html techniques that you can use along with the "mailto:"
Thanks Rey - I've changed send mail to open URL, but then just get asked for a URL (see attached).
I'm not sending email through a website - I'm sending it directly from my own PC.
Am I being thick? (It won't be the first time!!)