There are ways to use multiple milters with Postfix.
Milter Manager
For more details see the References.
References
- milter manager 0.7.0 http://www.mail-archive.com/postfix-users@postfix.org/msg06625.html
- milter.org – an interactive catalog of sendmail mail filters – https://www.milter.org/developers/api/xxfi_connect
- Postfix Mailing List Discussion http://archives.neohapsis.com/archives/postfix/2009-03/1525.html
- Milter Manager http://milter-manager.sourceforge.net/
Using multiple milters