Error installing Courier and policyd RPMs

[lblake]

I'm installing on CentOS 5.5 x86_64. I get this error when trying to install the Courier and the policyd RPMs:

[root@localhost tmp]# rpm -Uvh courier-* policyd-weight-*
warning: courier-authlib-0.63.0-1.el5.mf.i386.rpm: Header V4 DSA signature: NOKEY, key ID 5660e21b
error: Failed dependencies:
/usr/bin/expect is needed by courier-authlib-0.63.0-1.el5.mf.i386
/usr/bin/expect is needed by courier-authlib-0.63.0-1.el5.mf.x86_64

Any help appreciated.