Send & Receive Issues

Fix Outlook Error 451 4.7.650: Outgoing Email Messages Queued

Guest Writer Sep 28, 2026 869 views

Question details

Users are unable to send emails, and outgoing messages remain stuck in the outbox with an error regarding IP reputation.

How to Fix Outlook Email Error 451 4.7.650 (Messages Queued)

Product: Microsoft Outlook
Device & OS: not provided
Scenario: Attempting to send outgoing emails to recipients.
Observed behavior: Incoming email works normally, but outgoing messages remain queued and display the warning '451 4.7.650, temporarily rate limited due to IP reputation'.

Before you start

Ensure you temporarily stop trying to manually resend the queued emails, as repeatedly attempting to send messages during a rate limit can further penalize your IP address.

Solution 1Recommended

Test Email Sending via Outlook on the Web

Use the web version of Outlook to determine if the IP reputation error is isolated to your local desktop client or if it affects your entire email server.

Error 451 4.7.650 generally indicates a server-side or sender reputation issue rather than a problem with the Outlook desktop application itself. Testing on the web helps isolate the root cause.

Log into Outlook on the web

Open your preferred web browser and navigate to https://outlook.office.com/ to access your webmail.

Compose a test message

Create a new email and address it to a trusted contact or an alternate email address you own.

Send and monitor

Click Send and check if the email is successfully delivered or if it returns the exact same 451 4.7.650 bounce-back error.

Test Email Sending via Outlook on the Web

Server-side confirmation: If the email fails on the web as well, the issue is confirmed to be with your mail server's IP reputation, which requires administrative intervention.

Solution 2

Contact Microsoft Support or Your Email Administrator

If the rate limit persists across all platforms, you must escalate the issue to server administrators to clear your IP reputation.

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Frequently Asked Questions

What exactly does error 451 4.7.650 mean?

This error signifies that the recipient's email server has temporarily blocked or rate-limited your outgoing messages. It occurs because the sending IP address has developed a poor reputation, often due to suspicious activity, bulk mailing, or spam originating from that IP.

Should I keep trying to resend the queued emails in Outlook?

No. You should not repeatedly attempt to resend the queued messages. Continually hitting the recipient server while rate-limited can worsen your IP reputation and prolong the temporary block.

How long does a temporary IP rate limit usually last?

Temporary rate limits due to IP reputation can last anywhere from a few hours to 24 hours. The block will generally clear once the suspicious activity stops, but manual delisting by an administrator might be required for faster resolution.

Can using a VPN cause the 451 4.7.650 error?

Yes. If you are connected to a VPN, you are sharing an IP address with many other users. If another user sent spam from that same VPN IP, the server's reputation will drop, affecting your emails as well. Try disconnecting your VPN and sending the email again.

Outlook & Email Problems