When naming templates for ActionMailer 3 remember that the naming format has changed.

Templates used by in the form method.text.plain.erb and method.text.html.erb. They now take the form method.text.erb and method.html.erb.

This bit me with a lot of frustration, since it won’t automatically render the the old form. I only realised what was happening when I tried to manually render it and got a deprecation warning in the logs.