Dovecot authorization failure

Question

I have set up an mail server on Ubuntu 14.04 basing on Dovecot and Postfix. So far, everything works well with my first user (in my case "webmaster"). Now I have added some more users but I cannot do any query on them by using Thunderbird or any other mail program.

So I have tested my database with

doveadm user username

and I got a positiv result. But by using

doveadm auth test username

and after entering the correct password, I get the message "Auth failure". The logfile tells me

dovecot: auth-worker(1307): Debug: sql([e-mail]): SHA512-CRYPT(MyPassWd) != '$6$a.vRay8m***

But by testing this announcement with

doveadm pw -t {SHA512-CRYPT}hash

dovecot says me that the password is correct. So, does anyone know where the problem may might be?