CentOS does not use yum to install imapsync as Debian with apt-get, so that you must follow these steps:

perl -MCPAN -e "install Test::Inter"
perl -MCPAN -e "install Parse::RecDescent"
perl -MCPAN -e "install Getopt::Long"
perl -MCPAN -e "CPAN::Shell->force(qw(install Date::Manip));"
perl -MCPAN -e "CPAN::Shell->force(qw(install Mail::IMAPClient));"
perl -MCPAN -e "CPAN::Shell->force(qw(install Term::ReadKey));"
wget http://packages.sw.be/imapsync/imapsync-1.350-1.el5.rf.noarch.rpm
rpm -i --nodeps imapsync-1.350-1.el5.rf.noarch.rpm

Reference: imapsync web site