Echange 2007

I upgraded my exchnge 2003 to 2007. but some of the multifunction printers stopped sending e-mails (Scan to E-Mail) others continue working normaly. i changed the SMTP IP to the new one 2007 on those printers. what confused me that some is working normal but others not. those who are not working if I return the old SMTP IP (Exch. 2003)they will work normally.
thanks