We use google for our domain email. In order to handle uploads via email on this same domain we simply create a new account and send emails to this account. You then can have a hook (imap push) in google imap to detect when an email is received per account/box and process is right away. Or you can just run a cron every minute the check if new emails have been received. We then fire a script that pulls the email via imap, and then processes the emails/images into json format for use.

This allows us to keep everything on google and we do not need move our MX somewhere else. Also we keep our "upload" email on the same domain.

Pretty simple solution with no additional costs.