Strange Error: Password data is not valid for scheme SHA256. Please help me resolve it.

[Alexander Dalloz]

Am 23.07.2017 um 17:50 schrieb david.madman2 at vfemail.net:
> My /var/log/mail.log shows:
> 
> Jul 22 18:40:48 www dovecot: auth: Error: 
> passwd-file(test at domain.com,46.xxx.xxx.xxx,<wZoHUuxU6IAu9j4y>): Password 
> data is not valid for scheme SHA256: Input length isn't valid (0 instead 
> of 32)
> Jul 22 18:41:00 www dovecot: message repeated 2 times: [ auth: Error: 
> passwd-file(test at domain.com,46.xxx.xxx.xxx,<fGoHUuxU6IAu9j4y>): Password 
> data is not valid for scheme SHA256: Input length isn't valid (0 instead 
> of 32)]
> Jul 22 18:41:02 www dovecot: imap-login: Disconnected (auth failed, 3 
> attempts in 14 secs): user=<test at domain.com>, method=PLAIN, 
> rip=46.xxx.xxx.xxx, lip=139.xxx.xxx.xxx, TLS, session=<fGoHUuxU6IAu9j4y>
> 
> What does "Password data is not valid for scheme SHA256: Input length 
> isn't valid (0 instead of 32)]" mean? I assume that there is some kind 
> of a mismatch between the way I generated the password with doveadm and 
> entered it in passwd.db and the way I entered the non-hashed password 
> into the password field in the new account section of Thunderbird.

It means that dovecot expacts to verify a 32 byte long password hash. 
What it detects has a size of 0 byte. You haven't shown an example line 
of your passwd.db file, but I would guess you build it up not correct.

See

https://wiki.dovecot.org/Authentication/PasswordSchemes

Alexander