550 5.4.5 Daily sending quota exceeded
This one comes back when you send through Gmail, not to it. The Google account you are relaying from has used its daily outbound allowance: 500 messages a day for a free Gmail address, 2,000 for a Workspace user, and 10,000 recipients a day for the SMTP relay service. Everything after the limit is refused until the rolling 24-hour window moves on.
What the server replies
550-5.4.5 Daily user sending limit exceeded. For more information on Gmail 550 5.4.5 sending limits go to https://support.google.com/a/answer/166852
- Sent by
- Gmail and Google Workspace
- Type
- PermanentRetry fails
- About
- Rate limits and quotas
- Enhanced code
- 5.4.5
Who sends it
smtp.gmail.com and smtp-relay.gmail.com when an authenticated account submits a message past its quota. Apps and scripts that use a Gmail account as their outbound SMTP server see it most.
Why it happens
- A website, CRM or script is sending notifications through a personal Gmail account that was never meant for volume.
- A newsletter went out through Workspace to more recipients than the per-user limit allows.
- A new Workspace account is in its trial period, where limits are lower.
- Many messages were sent to invalid addresses; bounces count against the quota and Google lowers limits for accounts with high bounce rates.
How to fix it
Wait for the window
The limit is rolling, not midnight-based. Sending resumes as the oldest messages in the last 24 hours age out. Do not create a second account to route around it; Google suspends accounts for that.
Move application mail off Gmail
Gmail accounts are for people. Point your app at a transactional email service with its own domain authentication and no per-mailbox daily cap.
Use the SMTP relay service for Workspace
Workspace admins can enable the SMTP relay service, which carries a 10,000-recipient-per-day limit per user instead of 2,000 and is intended for devices and applications.
Check it yourself
These free tools show the records and connections behind this code for your own domain or server.
Related codes
- 535 5.7.8 Authentication credentials invalid / Username and Password not acceptedThe server rejected the login.
- 530 5.7.0 Authentication required / Must issue a STARTTLS command firstThe server will not go any further until the client does something it has not done yet.
- 454 Throttling failure: Maximum sending rate exceededYour application is submitting to SES faster than the account's per-second sending rate, or has used its 24-hour quota (the wording is then "Daily message quota exceeded").
Sources
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Other free tools
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- DMARC report analyzerDrop in a DMARC aggregate report and see who is sending as your domain and whether they pass.
- SMTP connection testerConnect to any SMTP server, check TLS and the login step, and see each stage with its timing.
- Email header analyzerPaste raw headers to see every hop, where the delay was, and whether SPF, DKIM and DMARC passed.
- Email address validatorCheck whether an address is well formed, whether its domain accepts mail, and whether it is disposable or a role account.