newlines in user registration mail don’t work

I have a question about adding a new line into the mail
(Registration Message Body)

The mails I send now, are all one single line. Although I have added -hard return- and -return- into the textfield, in the text these are visible but in the mail they are not visible. The mail is send as one continues line, without newlines.

How can I add newlines (returns) to my (registration) email?

thx