Note to self: Improve handbook with a small patch that helps in configuring default mta settings. Not a blocker per se.
Looks like this bug has been open for quite a while. If you'd like to contribute something about setting an MTA we would not be opposed. Please open a discussion on the relevant discussion page by following these instructions: https://wiki.gentoo.org/wiki/Handbook:Main_Page#How_do_I_improve_the_Handbook.3F Thank you.