A/B testing for email

Email is still the killer app for advocacy, election campaigns, and fundraising. NB needs to incorporate a way for groups who have enough people in their nation to give them statistically significant results to test different variables in their emails. NB needs to implement A/B testing for subject lines at the very least. It's becoming more and more frustrating to use NB at a high level and to leave something on the table because I'm just going with my gut, rather than being able to test various options. 

The experience of the Obama campaign certainly shows that often the gut picks of seasoned campaigners performed worse than other options. I'd like to avoid that trap and maximize the impact of the people in my nation.

Official response from Adriel Hampton

It's not yet a full solution, but a few months back we introduced random list splitting, which you can use to create groups of people for testing. Find it under "Split" after selecting a specific list.