added note in file telling which plugin uses it
added note in file telling which plugin uses it

salvis/qpsmtpd,sieutruc/qpsmtpd,priyadi/qpsmtpd,sieutruc/qpsmtpd,msimerson/qpsmtpd,msimerson/qpsmtpd,priyadi/qpsmtpd,smtpd/qpsmtpd,priyadi/qpsmtpd,smtpd/qpsmtpd,sieutruc/qpsmtpd,salvis/qpsmtpd