the dnn version doesn't use the app.config the appsettings from the app.config is included in the web.config and the mail.config is not needed because the emails are send through dnn not yaf

@dmiller can you try the updated dlls i post here:

http://forum.yetanotherforum.net/yaf_postsm55802_-Notification-for-topics-you-ve-posted-to--watched-or-marked-as-favorite--don-t-work.aspx#post55802 

if there is something wrong with the email sending it should be logged in the event log.