Gmail & Google Workspace SMTP Relay: The Complete Setup Guide

Published October 16, 2024 · Updated August 13, 2026 · SMTP & Deliverability

Google's SMTP servers can relay your outgoing mail — handy if you already live in Gmail or Google Workspace. There are two very different options, each with its own limits, and knowing which one you are using saves a lot of confusion.

The two Google SMTP options

Option	Server	Daily limit
Gmail SMTP (send as user)	`smtp.gmail.com`	~500–2,000
Workspace SMTP relay	`smtp-relay.gmail.com`	Higher, per policy

What the Workspace relay server is

Unlike sending as one user through smtp.gmail.com, the relay server (smtp-relay.gmail.com) is authorised at the domain level by a Workspace admin. It supports higher throughput and lets multiple systems — printers, scanners, line-of-business apps — send under your organisation's umbrella, not just one mailbox.

How to set it up

In the Google Admin console, open Apps → Gmail → Routing and configure the SMTP relay service.
Authorise your sending IP addresses (or require authentication).
Point devices and apps at smtp-relay.gmail.com on port 587, STARTTLS — or smtp.gmail.com for a single-user setup, authenticating with your Google account (an app password if 2-step verification is on).
Confirm SPF and DKIM include Google so mail is trusted.

Still a business tool

Even the Workspace relay lifts the ceiling, but it is built for internal and business mail, not marketing campaigns — and Gmail's single-user SMTP caps out fast. For real bulk volume, a dedicated SMTP with its own IP is the way.

Tip: Keep Gmail or Workspace for everyday business mail, and send bulk or marketing campaigns from a dedicated IP with no caps and automatic authentication.

Checking your Workspace admin settings
If relay mail is not arriving as expected, the Admin console's Gmail routing logs (Reporting → Email Log Search) show exactly what happened to a specific message — often faster than guessing at a configuration issue from the sending side alone.
Note: Keep your Workspace admin console bookmarked for quick access to routing logs — useful the moment something needs troubleshooting rather than searching for it under pressure.
If your organization uses multiple Workspace domains, keep the SMTP relay authorization settings for each documented separately — a setting correct for one domain is not automatically applied to another.
Related reading: What is SMTP relay · Free SMTP relay options · Office 365 SMTP relay

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Frequently asked questions

What is the Gmail SMTP relay server?

smtp-relay.gmail.com, the Google Workspace service that lets your domain's devices and apps relay mail at higher volume, authorised by an admin.

How is it different from smtp.gmail.com?

The relay is domain-authorised and supports higher throughput and multiple senders; smtp.gmail.com sends as a single user with lower caps (roughly 500–2,000/day).

Can I use Google's SMTP relay for marketing email?

It is not intended for marketing blasts. Use a dedicated SMTP with its own IP and no caps for bulk campaigns, and keep Google for business and transactional mail.