Plone 2.0.3 Error global name ‘to’ is not defined

This is a (easily fixed) bug with 2.0.3

see:-
http://plone.org/collector/3209
http://plone.org/documentation/errata/plone-2-0-3

Basically you need to edit the file Products/CMFPlone/PloneTools.py (on windows usually C:Program FilesPlone 2DataProductsCMFPlonePloneTools.py). Open this in a text editor (you’ll need one which open UNIX style files – notepad will be all over the place), then change line 89 to

 if not self.validateEmailAddresses(mto):

then you will need to save the file and restart plone.