@kuovonne’s approach using one of the glue-factories works and there are other ways as well.
I have three clients running Script Block processes that leverage Gmail accounts. It requires that you create a servlet in Google Apps Script (in the Gmail account where you want to send emails from) and an HTTP POST from the Script Block to the servlet. Lastly, a simple script in Google Apps Script that listens for the HTTP POSTS from the Script Block and transforms the payload into an email message and sends it.
Whew! Zapier might be a whole lot easier, but if you need a custom process that you own, can brand, and control the data flow - Google Apps Script is one pathway.