550 5.4.5 high
550 5.4.5 Daily User Sending Quota Exceeded (Gmail / Workspace)
The account hit Gmail's rolling 24-hour recipient cap; outbound mail stays blocked until the window clears, with no midnight reset.
What you see
550 5.4.5 Daily user sending limit exceeded. 550-5.4.5 Daily user sending quota exceeded. 550 5.4.5 https://support.google.com/mail/?p=DailyLimitExceeded
What’s actually happening
Mail that was flowing all morning suddenly bounces with 550 5.4.5, and every new send fails the same way. It counts recipients, not messages — one email to 100 people burns 100 against the cap. Waiting until midnight doesn't help; the limit is a rolling 24-hour window, so capacity returns gradually as old sends age out. Free Gmail caps around 500 recipients/day, Workspace around 2,000.
Common causes
- A free Gmail account exceeded ~500 recipients in a rolling 24 hours
- A Workspace account exceeded ~2,000 recipients in a rolling 24 hours (relay caps differ)
- Large distribution lists or CC/BCC blasts where each address counts as one recipient
- An app, plugin, or CRM sending through the account in a tight loop and silently inflating the count
- A compromised account being used to send spam, which exhausts the quota fast and may also trigger a suspension
How to fix it
- Stop sending and wait out the rolling windowThere's no force-reset. Pause all outbound for the account. Capacity frees up incrementally over the next 1-24 hours as the oldest sends fall outside the window — it's not a single midnight unlock.
- Check for a compromised accountIf you didn't send that volume, change the password immediately, review myaccount.google.com security activity, and revoke unknown app access. A quota hit you can't explain usually means something else is sending.
- Move bulk mail off personal SMTPNewsletters and campaigns belong on a dedicated ESP (SendGrid, Amazon SES, Postmark, Mailgun) with proper auth and unsubscribe handling. Gmail's limits exist to block exactly this use case.
- Trim recipients per messageReplace giant CC/BCC sends with smaller batches or an actual mailing list, and dedupe addresses. Fewer recipients per message stretches the daily allowance.
- Audit connected apps and integrationsA misconfigured plugin or script resending in a loop can drain the quota in minutes. Disable suspect integrations and watch whether the count stabilizes.
Stop it recurring
Route bulk and automated mail through a dedicated ESP, and keep per-account recipient volume well under the rolling 24-hour cap.
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