Hello to all. I think I'm not the only one that cannot use Mail since the upgrade to Sierra. I've googled Mail problems and this one comes on top: IMAP smtp account cannot connect. Mail asks for username and password and how many times I do it, smtp account is still disconnected. I found some useful information on different sites and followed the instructions but nothing resolved the problem. As for now, I only can receive emails. I cannot send. Only my iCloud account works. I really need help and solutions otherwise I'll have to revert back to El Capitan to my big disappointment.