Not sending html mails


I have set up phplist on my brand new server. I have always used pommo until now but unfortunately this is so outdated (and no longer supported) that it will not work on php7
I am just sending out test mails at the moment.
I have set the mail to HTML but I keep getting it in plain test (Content-Type: text/plain; charset=UTF-8).
I have even installed the tinymce plugin to make sure that it is indeed in proper html, but to no avail, the mails are all plain text.
I have made a system template and chose that on the second tab (clearly also indicated there that the mail should be sent in html), but it keeps coming in in plain text. I only want to see the bullets in a list, but they do not show up. All html code is stripped from the mails.
What could be the issue here?

You should look up the contact, and make sure they are set to receive html emails.