The hunt list.

Leave this blank to send from your connected Gmail address. To send from a different business or domain address, you must first add it to Gmail as a verified sender: open Gmail → Settings → See all settings → Accounts and Import → "Send mail as" → Add another email address, then confirm the verification email Google sends you. Once it's verified, enter that address here. Until it's verified, Google automatically reverts the From address back to your Gmail. Google's step-by-step guide ↗