Alexandru Puiu10: 32 11.12.2016 
If you're having trouble signing in when you're trying to add a Yahoo Mail account to your phone, it's a good idea to know how to reduce the security of your Yahoo Account to fix them.
Yahoo had a very difficult year in 2016. There were many scandals involved, millions of user accounts started circulating online, only to later be bought by Verizon, a major US operator. . Unfortunately, too many details about the alleged acquisition are not yet known, but one thing is for sure. The CEO of the American company does not have many reasons to celebrate this end of the year.
However, many of us have made our first email address on Yahoo. In the meantime, you may have a Gmail address or a work email address, but that Yahoo address from 10 to 15 years ago is still active, provided you can still activate it. In an attempt to increase or regain the trust of users in its services, in a rather aggressive way, it has significantly increased the security of accounts and changed the authentication process. The problem is so serious that many Yahoo users who do not use a browser or an official mobile application of the company to access their email, could not log in, using the correct password. The frustrating part is that they didn't even get a conclusive error message, they just noticed that they had the wrong username or password.
The solution, though absurd, is to reduce the security of your Yahoo account, a process that can only be done through a PC or Mac. Using your favorite browser, go to yahoo.com/account/security. At the bottom, make sure that Allow apps that use less secure sign-in is checked or, if you have an account in English, "Allow apps that use less secure sign-in." Please confirm your choice and try using your Yahoo Mail account on iPhone, Android, Outlook or Thunderbird again. It should work now.