auth_debug                      = yes

auth_debug_passwords            = yes

auth_ssl_require_client_cert    = yes

auth_ssl_username_from_cert     = yes

auth_mechanisms                 = plain external

passdb {

    driver              = passwd-file

    args                = scheme=PLAIN username_format=%u /etc/dovecot/users

    mechanisms          = plain external

    override_fields     = nopassword

}

userdb {

    driver              = passwd-file

    args                = /etc/passwd

}