Updated to El Capitan 10.11.5 a few days ago and boom, I cannot send any emails from the Mail app any longer.
Wether t's from my Macbook Air or my iPhone 6.
Server is disconnected. Authorization has expired.
Tried getting rid of the SSL, saved the settings but if I close and reopen the app, boom, SSL is back on.
Changed the outgoing server to Gmail as I also have an account with them and can now send out mails from my mac account from the app on my Macbook. But cannot do this on my iPhone. Impossible. So this is no good long term solution.
Driving me nuts.
Attempted asking Apple support for help and they are totally ignoring me. How nice.
Went to Finder/Library to try and save the data from my mail boxes in the hope to erase the account and recreate it then re-import everything. But....It's not there........