Bounce-Mail Error: 550 5.7.1 Service unavailable; client [XX.XX.XX.XX] blocked

1. Someone wants to send you a message, but has received this error message.

This error basically means that our server has refused to accept the email message from the passing mail server listed with its client IP.

Detailled reasons for this rejection may also be in the error message. If these reasons are resolved, the message could be accepted on a new delivery attempt.

Although we refuse to accept this message, the reason for non-delivery is not with us, but with the delivering mail server or the sender of the message.

For security reasons, for example, we generally do not accept messages from senders or mail servers that are on blacklists, are not configured correctly, or are generally not authorized to send messages with the sender’s email address.

2. You want to send a message to someone and you receive this error message.

In this case we ask you to start a support ticket in the customer area and forward us this error message including all header data (see ‘How to forward a message with header data’).

Such a case should actually never occur, as our outgoing mail servers detect this rejection and handle it automatically by using a different IP address for sending.