[Centos] postfix with tls?

[support at ev-theol.uni-bonn.de (support@xxxxxxxxxxxxxxxxxxxx)]

hi all,
i tried to install postgrey for postfix and had to update postfix to version
2.1.
i added the following to /etc/yum.conf
[postfix-2.1-rhel3]
name=Postfix Mail Server for RedHat Enterprise Linux 3.0 - $basearch
baseurl=http://ftp.WL0.org/yum/postfix/2.1/rhel3/

after the update i have problems because the new version of postfix doesn?t
support SASL.
is there an postfix-tls rpm for CentOS 3? If not how can i remove postfix 2.1
and install the old version with TLS support?
thank you very much for your help