Send & Receive Issues

How to Fix Error 451 4.4.4 When You Cannot Receive Email

Natalie Taylor Oct 19, 2026 868 views

Question details

The user is unable to receive incoming emails due to a 451 4.4.4 temporary server error.

How to Fix Error 451 4.4.4 When You Cannot Receive Email

Product: Microsoft Exchange / Outlook
Device & OS: not provided
Scenario: Waiting for incoming messages from specific contacts or all senders.
Observed behavior: Incoming emails fail to arrive and trigger a 451 4.4.4 server error, while outgoing messages continue to function normally.

Before you start

Check your internet connection and verify with your IT department if there is any scheduled maintenance or known outage for your email server.

Solution 1Recommended

Check Mailbox Storage Quota and Spam Folders

Ensure your mailbox has enough storage space to accept new incoming messages and verify emails are not being misdirected.

A full mailbox or overzealous spam filters can sometimes mimic temporary server errors by rejecting or hiding incoming messages.

Log into Webmail

Open a web browser and log into your email account to bypass any local email client syncing issues.

Check Storage Settings

Navigate to your email settings and view your current mailbox storage usage. If the storage quota is full, delete old emails or large attachments to free up space.

Review Junk/Spam Folders

Check your 'Junk Email' or 'Spam' folders to ensure that incoming messages from specific senders are not being incorrectly filtered.

Check Mailbox Storage Quota and Spam Folders

Storage Limits: If you frequently hit your storage limit, consider archiving older emails or requesting a quota increase from your email administrator.

Solution 2

Isolate the Issue to Specific Devices or Senders

Determine whether the 451 4.4.4 error is a widespread server issue or localized to certain platforms or contacts.

Solution 3

Verify Email Service Status and Contact Support

Check for broader service outages and escalate the issue to technical support if local troubleshooting fails.

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Frequently Asked Questions

What does the 451 4.4.4 temporary server error mean?

This error code indicates a temporary communication or routing issue between email servers, which prevents incoming messages from successfully reaching your inbox.

Can I still send emails when encountering a 451 4.4.4 error?

Yes, typically this error only affects the routing of incoming messages. Your outgoing emails should continue to process and send normally.

How long does a temporary server error usually last?

Temporary server errors often resolve themselves automatically within a few hours once the sending or receiving email server fixes its connectivity issues.

What is an ATTR5 code in Microsoft Exchange?

The ATTR5 code is a specific diagnostic indicator included in Microsoft Exchange error logs. It helps IT administrators pinpoint the exact misconfiguration or routing failure causing the delivery issue.

Outlook & Email Problems