A mailto link is a kind of hyperlink (`<ahref=""></a>`) with special parameters that lets you specify additional recipients, a subject line, and/or a body text.
If you want to add a specific subject to that mail, be careful to add `%20` or `+` everywhere there's a space in the subject line. An easy way to ensure that it is properly formatted is to use a [URL Decoder / Encoder](https://meyerweb.com/eric/tools/dencoder/).
#### Adding body text:
Similarly, you can add a specific message in the body portion of the email:
Again, spaces have to be replaced by `%20` or `+`.