Once DKIM was setup (for help, see this guide) et verified successfully on mon domain I encore had to enable it in le AWS console at SES -> Domains -> DKIM
Once that was done mails to Gmail no longer show up avec le via bounces address.
Vous pouvez see it encore shows as mailed by: amazonses.com quand you view details of le sender mais c'est OK depuis c'est true.
Importantly, it shows as signed by our domain.
Hope that c'est as simple as enabling DKIM for you.