ports downgrade in FreeBSD

Last week, i had a job migrating mail server from exim to postfix, but sadly, till now, this job unfinished yet :(. The main problem was synchronizing mail user from different engine to the new one. Thats the first problem. I wont discuss it in here. And, the second problem is, antispam. On my new mail server, antispam consist of spamassasin,Fuzzy-OCR,clamav,maia,and sane-security. Maia is a virus and spam management system built on SpamAssassin and amavisd-new scanner. It mainly supports scanning for viruses, spam, banned attachment types and invalid mail headers. It gives users control over their email accounts and the ability to manage their own content filtering settings through a web-based interface. Confirmed spam and ham are used to automatically train SpamAssassin’s Bayes engine and these recognitions can be automatically reported to spam-monitoring networks. Sounds interesting, isn’t it ? When i configuring maia using existing ports, i had an error on dependency file :(. Finally, i downgrade maia.
How to downgrade ports in FreeBSD ? here is it :

1. First, install portdowngrade program :
cd /usr/ports/ports-mgmt/portdowngrade
2. install it :
make DEFAULT_CVS_SERVER=\”:pserver:anoncvs@anoncvs.tw.freebsd.org:/home/ncvs\” install clean
3. downgrade your ports :
portdowngrade {PORTNAME}

pretty easy right ?