SMTP Code: 451 4.1.8 Domain of sender address does not resolve

Products

• Messaging Gateway

Issue/Introduction

Messages are queued in the Delivery queue with a status indicating the domain of the sender address does not resolve. This occurs when the destination mail server attempts a DNS lookup for the sender's domain and fails.

Symptoms

• Messages remain in the Delivery queue.
• Delivery status shows: 451 4.1.8 Domain of sender address does not resolve.

Environment

• Product: Messaging Gateway
• Version:10.8 and later

 

Cause

The destination mail server is unable to find a valid MX or A record for the sender domain in public DNS.

Resolution

To resolve this issue, ensure the sender domain is correctly configured in public DNS:

1. Verify that the sender domain has a valid MX record.
2. If no MX record exists, ensure there is a valid A record.
3. Use external DNS lookup tools to confirm the records are reachable from outside your network.

Example

nslookup -type=mx example.com
Server:         10.0.0.53
Address:        10.0.0.53#53

Non-authoritative answer:
example.com     mail exchanger = 0 192.0.2.25

nslookup example.com
Server:         10.0.0.53
Address:        10.0.0.53#53

Non-authoritative answer:
Name:   example.com
Address: 192.0.2.15