During the PyLadies lunch here at PyCon, I heard 5 people stand up and say that they would not have given a talk if an individual (in many cases Jessica McKellar) hadn't pestered them repeatedly to give a talk. I saw later that someone else had heard this from 10+ people at the lunch.
Increasing speaker diversity is both about sending emails "to the right mailing lists" but it is also largely dependent on individuals reaching out to new (and veteran) speakers to get them to submit talks.
So - a lot of this work has to happen on multiple fronts at the same time - the CFPs need to go out to lots of lists, and individuals need to reach out to lots of individuals.
The only way I have seen this be consistently successful is if many people on the conference committee are all making individual requests to speakers, and the people making the requests are trusted by the talk submitters. It's a systemic issue involving visibility, trust, mentorship in general, talk submission mentoring, and mentorship of talk creation, rather than something that can be solved with adding additional places for CFPs to be sent. Several women commented that they might have cancelled their talk after arriving in Montreal if they had not had support from PyLadies and other community members hours before they gave their talks.
More diverse members of the conference committee, that have time to do outreach, that can reach into new communities that trust the person who is asking, is a critical step in the process of increasing diversity.