InfoPath Dev

I've created form and published it on e-mail using Infopath 2010. But, when users with installed Infopath 2003 get the form they can't fill it. Is there any solution other then unification of Infopath software on every user station?

Have you tried first saving the form as an InfoPath 2003 form using the Save As dialog?

Infopath 2010 doesn't give option to save form as 2003, only 2007. Probably because e-mail publishing isn't available in 2003. But, because e-mail publishing is very interesting option for me I would really like to make it work. Any other suggestions?