4.7.0

Enhanced Status Code 4.7.0: Other Security or Policy Status - Temporary

Temporary failure High severity Security RFC 3463
What it means

Enhanced Status Code 4.7.0 means “Other Security or Policy Status - Temporary.” The receiving server has temporarily rejected your email for security or policy reasons. This is heavily used by Gmail and Microsoft for IP reputation-based throttling. Repeated 4.7.0 responses indicate a sender reputation problem that needs attention.

At a glance
Code4.7.0
Bounce typeSoft (temporary)
SeverityHigh
CategorySecurity
What to doQueued and retried automatically
StandardRFC 3463
What it looks like in your mail logs 
421-4.7.0 [203.0.113.10] Our system has detected that this message is suspicious due to the very low reputation of the sending IP address. To best protect our users from spam, the message has been blocked. Please visit https://support.google.com/mail/answer/188131 for more information. - gsmtp

What does 4.7.0 mean?

Enhanced status code 4.7.0 is one of the most important codes for email senders to understand. Gmail uses "421-4.7.0" when it detects suspicious sending patterns or low IP reputation. Microsoft uses it for similar reputation-based throttling. Yahoo returns temporary security blocks with equivalent codes.

When Gmail returns 4.7.0, it typically includes messages like "Our system has detected that this message is suspicious" or "IP not in whitelist for RCPT domain." This means Google is not blocking you permanently but is flagging your sending as potentially problematic. Your MTA should retry, and the message may go through, but repeated 4.7.0 responses are a serious warning.

If you consistently receive 4.7.0 from a major provider, it means your sending reputation needs improvement. Check Google Postmaster Tools for your domain reputation, verify all authentication records, review your sending patterns for spammy behavior, and ensure your lists are clean.

How 4.7.0 plays out

Your server attempts delivery
The recipient defers with a temporary 4.7.0 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 4.7.0 sits: soft vs hard bounce

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

Common causes of 4.7.0

  • IP address has low or unknown reputation with the receiving provider
  • Sending volume spike triggered throttling
  • New IP without established sending history (cold IP)
  • Previous spam complaints from recipients at this provider
  • Sending patterns match known spam behavior
  • IP was recently removed from a blacklist but reputation has not recovered

How to fix 4.7.0

  • Check your IP reputation using Sender Reputation Checker
  • Review Google Postmaster Tools or Microsoft SNDS for provider-specific reputation data
  • Warm up new IPs gradually over 2-4 weeks
  • Reduce sending volume temporarily to allow reputation to recover
  • Verify SPF, DKIM, and DMARC are correctly configured
  • Clean your email list of invalid addresses and unengaged recipients

Frequently asked questions

What does Gmail error 421 4.7.0 mean?
Gmail error 421 4.7.0 means Gmail has detected suspicious activity from your sending IP address or domain and is temporarily blocking your email. The full message typically reads: "Our system has detected that this message is suspicious due to the very low reputation of the sending IP address." This is a temporary (soft) bounce; Gmail is not permanently rejecting your mail but is throttling delivery due to reputation concerns.
How long does Gmail block an IP with 4.7.0?
Gmail's temporary blocks from 4.7.0 errors typically last from a few hours to 24 hours, though severe reputation issues can extend the block longer. Stop all outgoing email from the affected IP for at least 24 hours to avoid worsening the block. Your mail server should automatically retry delivery during this period. If the block persists beyond 48 hours, there may be a deeper reputation problem requiring investigation with Google Postmaster Tools.
How do I fix a 4.7.0 low IP reputation error?
Immediately reduce your sending volume from the affected IP and stop any campaigns that may be generating spam complaints. Verify your SPF, DKIM, and DMARC records are correctly configured. Use Google Postmaster Tools to check your domain and IP reputation scores. If reputation is low, implement a gradual warmup strategy by slowly increasing volume over several weeks while maintaining high engagement rates and low complaint rates. Ensure your email lists are clean and opt-in.
Is 4.7.0 the same as being blacklisted by Gmail?
No, 4.7.0 is a temporary rate limit, not a permanent blacklist. The "4" in the status code indicates a transient failure, meaning Gmail will accept your email once the issue is resolved. A permanent Gmail block would return a 5.x.x code. However, if you repeatedly trigger 4.7.0 errors without fixing the underlying reputation problem, Gmail may escalate to permanent rejection. Monitor your sending reputation proactively using Google Postmaster Tools.

Related bounce codes

421 Service Not Available - Try Again Later 5.7.1 Delivery Not Authorized - Message Refused 5.7.26 DMARC Authentication Failed

Sources & further reading

RFC 3463 · The standard that defines this reply code Gmail SMTP errors and codes · Google Workspace reference for 421 4.7.0 reputation-based blocks Yahoo Sender Hub SMTP error codes · Yahoo reference for temporary TS-class deferrals returned with 4.7.0
Reviewed by Jennifer Jackson, Email Deliverability Analyst · June 2026 ← All bounce codes