After Plone 2.0.2 a review of some of the other places that email could be sent from was undertaken. This included a look at CMF. A new release of the CMF, version 1.4.4 was made as a result.
For those users who cannot upgrade to Plone 2, this release has been made available. This is a recommended upgrade for all users. Installers have not be made available, instead you'll have to install from source.
There is a tarball available here: "Plone 1.0.6":http://prdownloads.sourceforge.net/plone/Plone-1.0.6.tar.gz?download
Take the contents of the tarball and copy them into the 'Products' directory of your Plone instance and then restart.