550 5.1.1: Mailbox Does Not Exist
The 550 5.1.1 bounce error means the recipient email address does not exist. Learn why it happens, what Google and Microsoft return, and how to fix it.
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550
5.1.1
Mailbox Does Not Exist
Very Common
🔢 Enhanced Status Code Breakdown: 5.1.1
| Component | Value | Meaning |
|---|---|---|
| Class | 5 | Permanent failure (Hard bounce) |
| Subject | 1 | Address / Destination |
| Detail | 1 | Mailbox Does Not Exist |
Per RFC 3463 Enhanced Mail System Status Codes. Class (X) = severity, Subject (Y) = category, Detail (Z) = specific condition.
💬 What This Error Means
We've all been there: you send an email and it bounces back because the address just doesn't exist. This is the digital version of 'Addressee Unknown.' It usually happens because of a simple typo, or perhaps the person has moved on and their old account has been closed.
Common Causes
- A simple typo in the email address (like .con instead of .com)
- The person has left the company and their account was deleted
- The recipient changed their email address but didn't set up forwarding
- The domain is correct, but this specific person doesn't have a mailbox there anymore
How to Fix This
- Take a close look at the address for any obvious spelling mistakes
- If you have another way to contact them, double-check if their email has changed
- Remove this address from your mailing list, since it doesn't exist, it will just keep bouncing
- If you were just given this address, verify it with the person one more time
📚 Official Documentation
Google returns: "The email account that you tried to reach does not exist. Please try double-checking the recipient's email address for typos or unnecessary spaces."
📖 Google Workspace / Gmail documentation → Browse all Google Workspace / Gmail error codes →Microsoft 365 returns: "Recipient not found by SMTP address lookup." Check the address in the GAL if sending to an internal mailbox.
📖 Microsoft 365 / Outlook documentation → Browse all Microsoft 365 / Outlook error codes →Yahoo returns: "No such user here." This is final. The address does not exist on their system.
📖 Yahoo / AOL documentation → Browse all Yahoo / AOL error codes →📋 Real-World Example Messages
These are real bounce message formats you might receive. Paste yours into the Bounce Decoder for instant analysis.
From: Mail Delivery Subsystem <[email protected]> Subject: Delivery Status Notification (Failure) Content-Type: message/delivery-status Final-Recipient: rfc822; [email protected] Action: failed Status: 5.1.1 Diagnostic-Code: smtp; 550 5.1.1 The email account that you tried to reach does not exist.
550 5.1.1 User unknown 550 5.1.1 <[email protected]>: Recipient address rejected: User unknown in virtual mailbox table
🔗 Related Error Codes
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