The misterious uuencode.1p.gz file is a manual page, as you can see from its location.
Looking at the output of the yum command, it looks like the package has not be found nor installed. I cannot tell where the uuencode man page comes from, but you can always find out by
rpm -qf /usr/share/man/man1p/uuencode.1p.gz
maybe it comes from a collection of unix man pages, even if the package has not been installed.
Anyway, why don't you try to install the uudeview
package? It is available for CentOS and provides the required functionality. For example to send a mail with a properly encoded attachment, you can use something like
uuenview -b -m <email_address> -s <subject> -a <file_to_attach>