https://rhn.redhat.com/errata/RHSA-2004-654.html refers

Updated files :-

updates/i386/RPMS/squirrelmail-1.4.3a-7.EL3.centos.1.noarch.rpm updates/i386/SRPMS/squirrelmail-1.4.3a-7.EL3.centos.1.src.rpm

To update run 'yum update squirrelmail'

These files are on mirror.caosity.org now and should be on local mirrors within a few hours.

Lance