What is the right way to embed an image into email using Rails?
I don't know much about rails, but I've worked on projects in C# that create emails and then insert them in a users inbox via the Google APIs. To create the email, I had to generate the email string from scratch. If you enable multipart for the email, then the image bytes will be included in a multipart section using base64 encoding.
You may want to check out the TMail and RubyMail packages to see if they support these actions for you.