Are you on hotmail/msn/live/outlook perchance? I believe they are having issues because a number of us can no longer access our email with eM Client as well as other apps and email clients.
Oh Great. I’m also having the ‘Server says failed’ problem, asking for password, which I know is correct. I have changed password several times, MS Outlook Office works at work with my Hotmail account, mobile phone app works with that Hotmail account, so it can’t be a server problem. It’s only Em Client that does not work.
I have been having the issue for about a week now. I, too, assume it is a Hotmail issue, and hoping someone can let us know what is going on.
I’m having the same issue. For me, started 21 Nov @ 9:51 pm US Central. 
Same problem repeatedly over the last 3 days with my Hotmail.co.uk account. Also asks for my password (error message: “password required”) despite entering the correct password repeatedly. The problem must be with eM Client
“The problem must be with eM Client” - exactly. No problems on phone, tablet or checking the email directly via the web. It is eM client. Just eM client ewith 2 hotmail accts. Other email accts working fine.
Fix it please - this been going on for about a week
Both me and my wife are having issues on our 2 computers (Win 10). Server says “failed”. We are trying to sync with Outlook. We have the latest version of eM client. Very frustrating. We were just thinking of upgrading to Pro also. What’s wrong with eM CLient?!
I have the same problem “failed” . from Spain. Help Please¡¡¡ (win xp)
Wonderful! After posting this, about another 7 or 8 people posted about the same problem. And tonight - my emClient is miraculously working on BOTH Hotmail accounts!
Thankyou emClient for listening to your users.
Began to work again 23 Nov around early AM.
The problem was actually with outlook’s servers. They confirmed this on their twitter yesterday. I had other email clients it was not working on, not just eM Client.