Update to the latest firmware at this link and try again.
If it doesn't work after the update, you would need to go through an intermediary server, something like SMTP2Go.
we tried to setup scan to e-mail with a Gmail account on a Xerox 6605 but it stucks on "processing...". We cannot delete the job and to make the printer work again we have to reboot it.
These are our settings, maybe something wrong related to SSL?