You can connect Gmail and have your app send through the Google account that approves the connection. That account can be a Google Workspace mailbox. The connection uses Google's API; it does not require your app to open an SMTP connection.
Set it up
Open Integrations, find Gmail and connect the account you want to send from. Review Google's consent screen and confirm the mailbox before approving. Your organization's Google Workspace policies can restrict which connections it allows.
Ask the builder to use that Gmail connection for the specific email your app needs to send. Test with your own recipient address and check the actual sender before publishing.
Sending and replies
A connected mailbox is different from the app's built-in shared sender. Connecting Gmail does not silently move every existing email to Gmail: the app's sending code must use the connection.
Sending uses credits, and the rate depends on the connection used. A request accepted for sending is not a guarantee of inbox delivery.
Reply-To handling differs between the available Gmail connection paths. If a custom reply address matters, test the received message rather than assuming the connection supports it. For a dedicated sending domain, see Sending email from your own custom domain.