If you want to protect the poor Windows users that continually suffer from these things, use clamav available in the repositories.
This can be installed via the synaptic package manager in Ubuntu. Simply mark it for installation and apply. It runs silently in the background and you can forget it.
Any content received by email from Windows users will then be scanned and if anything nasty is detected, it will be taken care of, prior to you passing it on to anyone else.