Domain email authentication and profile photo

We use Gmail to send emails with our domain email address. Recently our recipients are getting a warning message from all our emails, see attached screenshot. Would like this to be resolved for all our domain emails.

We would also like to set up profile photos for our domain email. We have set a profile photo in our gmail but this does not come up when we send it using our domain email address.

Let me know if you need more info, thanks!