Modern Layout - Messed up tabular listing on inbox page

[gridhead]

The way that the mails are listed is clearly messed up. All the columns of both the mail lists are supposed to come in line.

Notes

• This build is not available in the master branch. Check out the modern-layout branch.
• The HTML5 template can be found in the templates directory by the name inbxpoge.html.
• The boilerplate put to use is heavily based on Bootstrap 4. This might give you a headstart.