Hello guys,
Thanks for replay.
In our offices, Workcentre 7720 only works with smtp.gmail.com on port 465 and TLS/SSL. In the other hand, Workcentre 6605 since last 25th only works with smtp.googlemail.com (different IP) on 587 and STARTTLS. Both models uses same email account on Google Apps. Two step auth is not enabled.
I hope this helps those in need 
Javi