5.4.5

Enhanced Status Code 5.4.5: Daily Sending Limit Exceeded

Temporary failure High severity System RFC 3463
What it means

Enhanced Status Code 5.4.5 means “Daily Sending Limit Exceeded.” The sending account has exhausted its daily quota. Google numbers it 5.x, but the limit resets on a rolling 24-hour window, so this is a wait rather than a permanent failure and the address must not be suppressed.

At a glance
Code5.4.5
Bounce typeSoft (temporary)
SeverityHigh
CategorySystem
What to doQueued and retried automatically
StandardRFC 3463
What it looks like in your mail logs 
550 5.4.5 Daily user sending limit exceeded

What does 5.4.5 mean?

Google returns 550 5.4.5 when a daily sending limit has been exceeded, either the per-user limit or the SMTP relay limit for the account. The registry assigns X.4.5 to mail system congestion, which is a capacity condition affecting everyone; Google's usage is a quota that belongs to your account specifically.

The limits are real and lower than most people expect. A Google Workspace user sending through the standard interface or SMTP is capped at a few thousand recipients per day, counted by recipient rather than by message, so one message to two hundred people consumes two hundred of the allowance. The SMTP relay service has a separate and larger limit. Hitting either produces this code and stops all further sending from that account until the window rolls.

The rolling window is the detail that catches people. The quota does not reset at midnight; it is evaluated over the preceding 24 hours, so an account that exhausted its limit at two in the afternoon recovers gradually from two in the afternoon the next day rather than all at once at midnight. Waiting for a calendar day to turn does not restore sending.

How 5.4.5 plays out

Your server attempts delivery
The recipient defers with a temporary 5.4.5 reply
Your server queues the message and retries on a back-off schedule
It delivers on a later attempt, or becomes a hard bounce if it keeps failing

Where 5.4.5 sits: soft vs hard bounce

Soft bounce (4xx) Hard bounce (5xx)
NatureTemporaryPermanent
SMTP class4xx5xx
What to doLet it retrySuppress the address
Recoverable?OftenNo
5.4.5 is✓ this code

What each provider means by 5.4.5

A registered code does not oblige a provider to use it that way, and the large ones diverge. Match the wording in your own bounce, not the definition above.

Gmail Daily user sending limit, or daily SMTP relay limit, exceeded Reference
IANA registry The registry assigns 5.4.5 to mail system congestion Reference

Common causes of 5.4.5

  • The account exceeded its daily recipient limit, counted per recipient rather than per message
  • A message with a very large recipient list consumed the entire allowance at once
  • The SMTP relay limit for the account was exceeded
  • Automated sending from a user mailbox rather than a purpose-built relay
  • Several applications share one account and their volumes add up
  • A retry loop resent the same messages repeatedly and consumed the quota

How to fix 5.4.5

  • Move bulk sending off a user mailbox and onto a transactional provider or the SMTP relay service
  • Count recipients rather than messages when estimating your usage
  • Wait for the rolling 24-hour window rather than expecting a reset at midnight
  • Give each application its own sending identity so one cannot exhaust another
  • Check for retry loops, which can consume a daily quota in minutes
  • Split large sends across days, or use a service designed for the volume

Frequently asked questions

What does 550 5.4.5 mean from Gmail?
It means the sending account has exceeded its daily sending limit. Google Workspace caps how many recipients an account can send to in a rolling 24-hour period, and the SMTP relay service has its own separate limit. Once the cap is reached, all further sending from that account stops until the window rolls forward.
When does the limit reset?
On a rolling 24-hour basis, not at midnight. If you exhausted the quota at two in the afternoon, capacity returns gradually from two in the afternoon the following day. Waiting for the calendar date to change does nothing, which is why senders often believe the limit is stuck when it is behaving normally.
Are limits counted per message or per recipient?
Per recipient. A single message addressed to two hundred people consumes two hundred of the allowance. This is the most common reason an account hits the limit unexpectedly: the message count looks modest while the recipient count is enormous.
How do I send more than the limit allows?
Stop sending bulk mail from a user mailbox. Google Workspace accounts are built for a person's correspondence, not for campaigns or transactional volume. Move that traffic to Google's SMTP relay service, which has higher limits, or to a transactional provider built for the purpose, and keep the user mailbox for actual mail.
Why does the registry say 5.4.5 means congestion?
IANA assigns X.4.5 to mail system congestion, a capacity condition affecting all senders. Google repurposed the number for a per-account quota, which is a different thing entirely. If your bounce came from Google and mentions a daily limit, read it as quota rather than congestion; a genuine congestion deferral would be 4.4.5.

Related bounce codes

5.2.1 Mailbox Disabled or Not Accepting Messages 4.2.1 Mailbox Disabled or Rate Limited - Temporary 5.5.3 Too Many Recipients 5.7.1 Delivery Not Authorized - Message Refused 4.7.28 Mail Flood Detected - Temporary Rate Limit

Sources & further reading

RFC 3463 · The standard that defines this reply code Gmail SMTP errors and codes · Google Workspace reference for every code Gmail returns IANA registry · The authoritative list of enhanced status codes and their meanings
Reviewed by Jennifer Jackson, Email Deliverability Analyst · June 2026 ← All bounce codes