i had used CEmags along with other free email programs and i had VERY good results. I noticed for certain traffic sources, only cemags can turn a good ROI. The matrix page as pheer said converts very good. I made some alternative of it that gives you a slightly better ratio,but im keeping it for myself
In general free email programs will make you pretty much the same kind of money with some expections on certain traffic sources. You'll see the ones complaining for bad stats and ratios they do it across all programs and vice versa. I can show you below 1:8 ratios among all email programs.