550 5.7.1 service unavailable, client host blocked using spamhaus.

Products

• Messaging Gateway

Issue/Introduction

Outboud messages cannot be delivered due to the following SMTP error "550 5.7.1 service unavailable, client host blocked using spamhaus."

Resolution

Customers need to create a request to Spamhaus to get know the reason behind this. The issue can happen when the EHLO SMTP command shows different domain or hostname.