Moved cyrus plugins to the mail directory.
Prevent duplicate plugin name and reflect what the plugin really is doing.
Moved dovecot plugins to the mail/dovecot directory.
Moved j-chkmail mail filter plugin to the mail directory.
Moved all postfix plugins to the mail/postfix directory.
Moved powermta plugins to the mail/powermta directory.
Moved qpsmtpd plugins to the mail/qpsmtpd directory.
Moved zimbra plugin to the mail/zimbra directory.