Permanent failure — do not retry
SMTP 550 5.4.5
daily sending limit exceeded (Gmail)
SMTP 550 5.4.5 is Google's "daily user sending limit exceeded". Your Gmail or Google Workspace account has sent more messages or recipients than Google allows in a rolling day, and it will refuse further sends until the limit resets. It is about your account, not the recipient.
How it appears
550 5.4.5 Daily user sending limit exceeded.
550 5.4.5 Daily SMTP relay limit exceeded for user.
What causes it
- A campaign or mail merge was sent from an ordinary Gmail or Workspace mailbox.
- An app or script sending through your account sent more than expected.
- The SMTP relay service hit its own daily limit for the user.
How to fix it
In order — try the first one first.
- Wait for the limit to reset. Google's limits work on a rolling 24-hour window.
- Move bulk and cold sending to a dedicated sending service built for volume.
- Check the account for apps or scripts you did not expect to be sending.
- Do not remove the recipients. They were never contacted.
Common questions
- What does SMTP 550 5.4.5 mean?
- SMTP 550 5.4.5 is Google's "daily user sending limit exceeded". Your Gmail or Google Workspace account has sent more messages or recipients than Google allows in a rolling day, and it will refuse further sends until the limit resets. It is about your account, not the recipient.
- Should I retry a 550 5.4.5 error?
- No. 550 is a permanent failure, so the message will never be delivered no matter how many times you try. Remove the address — repeated sends to permanent failures are one of the main signals mailbox providers use to throttle a sender.
- How do I fix SMTP 550 5.4.5?
- Wait for the limit to reset. Google's limits work on a rolling 24-hour window.
Other 550 replies
- 550 5.1.1 — mailbox does not exist
- 550 5.7.1 — message refused by policy
- 550 5.4.1 — recipient address rejected, access denied
- 550 5.2.1 — mailbox disabled, not accepting messages
- 550 — mailbox unavailable
- 550 5.1.0 — address rejected, other address status
- 550 5.1.10 — recipient not found (Microsoft 365)
- 550 5.1.8 — bad outbound sender (Microsoft 365)
- 550 4.4.7 — message expired in the queue
- 550 5.7.25 — no PTR record for sending IP (Gmail)
- 550 5.7.26 — blocked, sender unauthenticated (Gmail)
- 550 5.7.27 — SPF authentication failed (Gmail)
- 550 5.7.28 — unusual rate of unsolicited mail (Gmail)
- 550 5.7.23 — SPF violation (Microsoft 365)
- 550 5.7.124 — sender not in allowed senders list (Microsoft 365)
- 550 5.7.509 — DMARC failed, policy reject (Microsoft 365)
- 550 5.7.606-649 — banned sending IP (Microsoft)
- 550 5.7.705 — tenant has exceeded threshold (Microsoft 365)
- 550 5.7.708 — traffic not accepted from this IP (Microsoft 365)
- 550 5.7.750 — blocked from sending from unregistered domains (Microsoft 365)
- 550 5.7.515 — authentication required for high-volume senders (Outlook.com)
- 550 5.7.1 S3140 — IP range on Outlook.com block list
Last reviewed 2026-09-11