Workspace SMTP relay and Gmail’s authenticated SMTP submission are different sending routes. Choose the supported route for the device or application rather than copying a server name and assuming its authentication and quotas are interchangeable.
Identify the sender and device capabilities
Determine whether the application sends as an individual mailbox or as an organization-managed system. Check its support for current authentication, TLS, and an approved network source.
Do not enable legacy username-and-main-password access. Google’s current transition guidance requires supported authentication for affected Workspace clients. An app password, where permitted and appropriate, is a separate restricted credential and is not a reason to disable two-step verification.
Compare the routes
Google documents smtp-relay.gmail.com for an administrator-configured relay. The administrator controls allowed senders, permitted source IP addresses or authentication, and TLS requirements. Relay limits differ from individual Gmail sending limits.
Gmail SMTP submission uses smtp.gmail.com and the authentication supported for that account and client. Google’s printer and app guidance gives specific permitted app-password setup where applicable. A device unable to meet the supported requirements may need a vendor update or a different approved route.
Keep the relay narrowly controlled
Do not choose unrestricted senders or broad IP ranges merely to make a test succeed. Google warns that allowing any address increases abuse risk. Account for shared or changing public IP addresses, which can make an IP-based rule much broader than one printer.
Test one harmless internal and external message through the chosen route, inspect authentication, and verify any required retention or logging. Store credentials securely and rotate them through the supported process when access changes. Record the server, port, TLS mode, authentication method, sender scope, and limits. Avoid treating a successful connection as proof that the route is safe for unrestricted production sending.
Browse Gmail & Google Account help
References
- Send email from a printer, scanner, or app | Gmail | Google Workspace Help
- Route outgoing SMTP relay messages through Google | Gmail | Google Workspace Help
- Transition from less secure apps to OAuth | Sync data | Google Workspace Help
Reviewed against the linked product guidance, standards, and identified vendor or public-authority guidance on October 29, 2026. Available options and screen labels can vary by account, device, region, and organization policy.