You can create custom links. If you want to create a link to start an email, I haven't been able to have the Qualtrics email function to be able to pass embedded data into that.

Can you give me an example of what that would look like in the body of an e-mail? Writing html in the e-mail body isn't doing it for me; is there a special syntax to start a custom link?

What kind of link are you trying to build? If you are using the Qualtrics email tool for a report, it is better to switch it the script view to type out the link (e.g Search Engine).

I'm building this under Edit Message in the Message Library. Looking to do something like this:
email link text

In the email body where I've referenced embedded data, the html source looks like this:
embedded data.

But this syntax isn't working for the 'mailto' link, it just shows up in the e-mail subject/body as ~{aed://embedded_data_a}.