Send from Gmail with your domain over SMTP
Add an address on your domain to Gmail's Send mail as, so mail you write in Gmail goes out through Unitpost from your verified domain.
Check the address can receive mail
The address must be on a domain you've verified in Unitpost. Gmail confirms it by emailing a code to that address, so it also needs an inbox or forwarding that you can read.
Open Send mail as
In Gmail go to Settings → See all settings → Accounts and Import. Under Send mail as, click Add another email address, enter your name and the address, then click Next Step.
Enter your Unitpost SMTP settings
SMTP Server smtp.unitpost.com Port 587 Username unitpost Password Your Unitpost API key Security Secured connection using TLS Use port 465 with Secured connection using SSL if you prefer implicit TLS. The username is always unitpost, not your email address.
Confirm the address
Click Add Account. Gmail checks the connection, then emails a confirmation code to the address. Enter the code to finish.
Send and verify
Compose a message, pick the address in From, and send. It shows up in your Unitpost Activity view.