Error: 550 5.1.1 : Recipient address rejected: User unknown in virtual mailbox table.
Article ID: 430190
Updated On:
Products
Issue/Introduction
The email is not delivered. The error code displayed in Track and Trace logs are as follows:
550 5.1.1 : Recipient address rejected: User unknown in virtual mailbox table.
Environment
Email security cloud
Cause
The potential cause of the issue may be as follows:
1. This error message indicates that the recipient email address does not exist on the mail server.
2. The message is rejected by recipient mail server.
3. The MX, SPF or DMARC settings might be misconfigured by the recipient.
Resolution
The issue isn't caused by Email security cloud. You must contact the recipient to resolve the reason of the issue. The email isn't blocked by Email security cloud but the server of recipient, or its security email product.
Additional Information
Another error that can be displayed is 421: domain does not resolve
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