The solution to import emails from the server Yandex

Mail was on our server. We moved on Yandex. After you add the mailboxes imported from the server emails. However the 1st box information is not transported at all (error when importing) and on the other was most likely transported partially. You need to recheck and figure out what is wrong. Google gives "wrong username or password". But we changed already on the server, and on Yandex, but no solution found.
Mail carried on Yandex 13.11, therefore, only since that day in the problem box displaying letters.
Will provide a list of mailboxes.