Intermittent IMAP Login failures - about 25% fail

Thu Apr 7 16:24:07 UTC 2016

On 07 Apr 2016, at 19:02, Mobile Phone <cell at eceb.co.uk> wrote:
> 
> pam(prtg.08dir,91.91.91.91): pam_authenticate() failed: Authentication
> failure (password mismatch?) (given password: YesThisWasTheCorrectPassword)
..
> Why it this bouncing 25% + of IMAP AUTH LOGINs?

PAM said that login wasn't allowed. PAM can have all kinds of plugins that can do all kinds of things. Maybe you have enabled some PAM plugin that denies the user's access even if the password is correct. Unfortunately there's no way to enable debugging for PAM. Try simplifying your PAM setup, or if you can't figure out anything else switch to passdb shadow.