Markdown is a writing format that converts from plain text to html and vice versa. The format buttons in Boxy allow to add html styling easily, but some prefer to use the markdown syntax to style their email.

Now that you're in Markdown mode, you can try to format text like this:

HTML | Markdown
--- | ---
## Header | ## Header
| *** (horizontal rule)
Bold | **Bold**
Italic | _Italic_ or *Italic*
Link | [link](https://boxyapp.co)
`Code` | `Code`
Quote | > Quote
List item | * List item

To find out more, check out CommonMark syntax guide and the original specification by John Gruber.