Please, if you do something regarding SA LEARN, don't forgot to move the sa-learn directory outside of the plugin tree. Right now, on each plugin update, content of that directory is flushed... And even if that directory is for volatile data, I would prefer see them outside of the plugin tree.
I also don't like the solution how it is implemented, and I have two different options how to learn mails and both don't need the sa-learn directory inside of the plugin.
I only have to figure out which one is better. Both have pros and cons.