HOWTO: Find a version of something
If it was installed by RPM you can use this shell command (as root) to find out what version you have installed of any program on your box.
Example for squirrelmail:
rpm --query -a | grep squirrelmail
And some others:
rpm --query -a | grep exim
rpm --query -a | grep sendmail
To see the entire list:
rpm --query -a
This isn't 100% because some programs are inside other packages. Like the "net-tools" package contains things like "ifconfig, netstat, route" and others.
For that you could use a command like this:
rpm --query -ai | grep -B 10 -A 10 netstat