Update mailer.rst

Co-Authored-By: Wouter J <[email protected]>

Author: weaverryan

mailer.rst

@@ -541,7 +541,7 @@ You can combine all filters to create complex email messages:
         {# ... #}
     {% endfilter %}
 
-This makes use of the :ref:`css Twig namespace<mailer-css-namespace>` we created
+This makes use of the :ref:`css Twig namespace <mailer-css-namespace>` we created
 earlier. You could, for example, `download the foundation-emails.css file`_
 directly from GitHub and save it in ``assets/css``.