I've built & configured the dovecot to use mysql as the passdb and userdb. However, dovecot-auth always claims that the username/password of mysql server is wrong (access denied by mysql server) during the connection. When I set the password to NULL, it can successfully connect to mysql server! I am 100% sure that I typed the correct password (by copy & paste), and I can successfully use this username/password connect to mysql server by mysqladmin and other mysql clients. I even wrote a C program which also successfully connects to mysql server. Furthermore, even I want to use pam_mysql in dovecot, the pam library also claims that it cannot connect to mysql server, but pam_mysql can be successfully used in postfix (exactly the same pam configuration, the same database, the same table, and the same username/password).

Can anybody give me a hint why? Thank you very very very very much.... Crying for help....