General :: Mysql Authentication Does Not Work

My system is

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We use courier mail server for pop3 mailboxes, and postfix for in/out mail delivery

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Now Pop3 users, could not authenticate with there username/pass

It does not work now, and I have this message in my log file

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I could see in my postfix.main

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And I could successful run query from mysql

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I tried to change the password for this user, insert new user to the same tables, but no success to authenticate

I suppose that the problem is authentication of courier mail demon (which in my mind ) should work with mysql 'mail' database in the way is postfix work

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I could not find any reference with courir demon to mysql database username,password to authenticate users..

So, my quetions is, if it's possible to tracert mysql db to find out if courier demon 'asking' for authentication, or is there any error with this, and which configuration file should be checked, in order to find out what authentication method is courier mail demon use for.