All whitespace within the `{% trans %}` block will be deleted. Therefore the email will be sent in one line like this

```
Hi d, You invited sdfdsf to create a profile on mozillians.org. Take a look at their shiny, new profile: http://127.0.0.1:8000/en-US/u/team/ Thanks for inviting a contributor to join our community directory!
The Mozillians.org team
```

To solve this you can create multiple `trans` blocks and leave the newlines out of them, like this http://pastebin.mozilla.org/4710333 (new lines are really important)