Pick the path that matches your volume

User-level SMTP works for individual senders below 2,000 messages per day. SMTP Relay is for higher volume and for sending on behalf of multiple addresses in your domain. Most agencies and operators should use SMTP Relay.

The cap difference is published in Google's official Workspace sending limits documentation - it is not a soft limit you can negotiate. Hitting it returns 550 Daily user sending quota exceeded and the user's outbound is paused for 24 hours.

Option A - User-level SMTP (App Password)

Same flow as personal Gmail but on a Workspace domain. The 2FA prerequisite is mandatory and your Workspace admin must allow App Passwords org-wide.

1. Sign in to myaccount.google.com as the Workspace user.
2. Confirm 2-Step Verification is ON under Security.
3. Visit myaccount.google.com/apppasswords.
4. Name it "Inflowave", click Create.
5. Copy the 16-digit passcode and paste into Inflowave with host smtp.gmail.com port 587.

If "App passwords" is hidden: Your Workspace admin disabled them. Two fixes - ask the admin to allow App Passwords org-wide (Admin console → Security → Authentication → 2-Step Verification → check "Allow users to turn on App Passwords"), or use the SMTP Relay path below instead.

Option B - SMTP Relay Service (10,000/user/day)

Only a Workspace super admin can configure this. Once configured, every user in the relay can authenticate via App Password OR (if you use a static egress IP) without any credentials.

1. Sign in to admin.google.com as a super admin.
2. Top-left menu → Apps → Google Workspace → Gmail → Routing.
3. Scroll to SMTP relay service and click Configure.
4. Name it (e.g. "Inflowave relay").
5. Under Allowed senders, pick "Only registered Apps users in my domains" (strictest, recommended). If you need to send from external addresses, "Only addresses in my domains" works.
6. Under Authentication, check Require SMTP Authentication if you will paste credentials in Inflowave. Check Only accept mail from the specified IP addresses if you have a static egress IP and want to skip credentials.
7. Under Encryption, check Require TLS encryption.
8. Click Save.
9. Wait up to 24 hours for propagation (usually it is live in minutes).

Sub-host gotcha: If you accidentally type smtp.gmail.com instead of smtp-relay.gmail.com in Inflowave, the connection authenticates against the user-level path and silently caps at 2,000/day. Triple-check the host before saving.

Connect to Inflowave

1. Inflowave → Settings → Email → Add sending domain → Custom SMTP.
2. Host: smtp.gmail.com (Option A) or smtp-relay.gmail.com (Option B).
3. Port: 587.
4. Username: Workspace email.
5. Password: the 16-digit App Password.
6. Save and send a test from the linked domain card.

Troubleshooting

Official sending limits

• 2,000 messages per user per 24h via smtp.gmail.com (user-level SMTP).
• 10,000 messages per user per 24h via smtp-relay.gmail.com (SMTP Relay).
• 100 recipients per single SMTP transaction - exceeding this returns 5xx on the transaction.
• 4.6 million recipients per organization per 24h.
• 319,444 recipients per rolling 10-minute window across the org.
• The 24-hour rolling window resets at midnight Pacific time.

Official sources

• Google Workspace Knowledge - Route outgoing SMTP relay messages through Google
• Google Workspace Admin Help - SMTP relay service: Route outgoing non-Gmail messages
• Google Workspace Admin Help - Gmail sending limits in Google Workspace (the 2k/10k/4.6M numbers)
• Google Workspace Admin Help - Set up your device or app to send mail through Google Workspace

Other provider guides

• Personal Gmail SMTP
• Microsoft 365 / Exchange Online SMTP
• SendGrid SMTP
• Amazon SES SMTP
• All providers at a glance (hub article)