Yet a "safe" email system is now gone. A better idea would be to move yourself and your encrypted email company to a country that will let you keep providing such a useful service (assuming there is one).
[1] RetroShare, BitMessage, I2P Bote, Freenet + Frost and some others, which haven't tried yet.
https://torrentfreak.com/kim-dotcom-will-move-mega-privacy-s...