Thank you so muchcpa networks usually divided into niches. what niche are you focusing on? email marketing is more of a traffic generation method. unless youre promoting email marketing websites, in that case going directly to the advertiser is best bet (ex aweber.com/affiliates.htm)
affposts & offervault 2 of my favorite sites for such research.
networks like peerfly CJ clickbank cpaprosperity are pretty broad with hundreds of offers.