We don't know if odoo is supposed to work that way, but when we send (eg.) a RFQ from odoo, and then when the supplier responds and we answer him in the (eg.) gmail email, then something is triggered and the supplier recives the email twice (one from odoo and one from gmail) but at different times (as odoo sends them at the next o'clock).

Is this an expected behavior? Is there a way to disable this second email? 

So far we have discovered that before odoo sends them you can access and cancel them if you go to (in dev mode) Settings->Technical->Email->Emails.

Any help is appreciated.

Thank you.