Common Error Codes found in Message Details

Common Email Delivery Error Codes

Situation – Looking in Message Details, found in Logs, the delivery status often shows error codes explaining why a message shows as bounced or deferred.

Solution – These Error Codes can provide clues that can assist an admin in troubleshooting and correcting issues with their mail system.

Delivery summary

Any time you see, “This message was rejected by its destination for reasons outside the control of Spambrella, and got returned to the sender”, this literally means that this is outside our control, and this issue must be with the Customer/Recipient server accepting the message.

452 4.3.1 Insufficient system resources

This normally means that the recipient/customers server doesn’t have enough resources to accept messages. Customer/recipient needs to resolve this issue before we can deliver the message.

550 5.7.1 : Recipient address rejected

The user email address is marked as invalid. This means normally you have SMTP Discovery enabled and the user is on the SMTP Discovery Invalid list. Remove this user from this list to resolve this issue.

550 5.1.0 sender rejected

The senders IP address is rejected due to a Blacklist/ wrong SPF. This is outside the control of Spambrella.

550 5.7.1 Relay Access denied

We are a closed relay system. This means if a user is in the Spambrella system we will deny access to any e-mail that is not registered.

For more information and understand on error codes please visit

Administrator Topics

Inbound Email: Not receiving emails from particular senders or sending domains.