This survey says that most political and social action email appeals take place after 6 pm:  http://www.emarketingandcommerce.com/article/political-social-action-organizations-prefer-later-hours-email/1?e=larry-kaplan@sbcglobal.net#utm_source=nonprofit-pro-today&utm_medium=enewsletter_continue_story6&utm_campaign=2015-03-27