At times, when you send mails to a certain recipient address, it may fail to deliver, giving the following error message:

An error occurred while trying to deliver this message to the recipient's e-mail address.
 Diagnostic information for administrators:

Remote Server returned Requested #571 Delivery not authorized message refused

Today we’ll see what this error means and how to fix it.

What is ‘571 Delivery not authorized message refused’ error

571 error is due to recipient server issues and it usually happens when the recipient mail server blocks mails from the sender mail server.

Email error 571 means the sender is not authorized to send to the destination, and can happen due to server-wide or domain-specific blocks.

This error message is specific to Microsoft Exchange server. The sender whose mail was rejected, will see the error 571 in the bounce mail they receive.

Email blocks can happen due to many reasons:

1. Sender IP address blocked in recipient server

Many recipient servers use custom Spam block tools such as Spamfilter or Antivirus to prevent spams reaching their server. Some servers have firewalls to block suspicious IP addresses.

If the sender mail server is detected as a source of spam and blocked by these tools, mails from that sender will be rejected and the error message ‘571 delivery not authorized message refused‘ is shown.

2. Sender IP address doesn’t have RNDS

To validate the sender mail servers for authenticity, many recipient servers look up for reverse pointers. An RDNS helps to verify that the sender is a valid and trusted one.

Due to this RDNS security restriction, recipient servers may reject mails from senders without RDNS and bounce emails with the error ‘571 Delivery not authorized, message refused‘.

3. Sender blacklisted in Spamlists such as Spamhaus

Some mail servers look up the Spam lists such as Spamhaus for server reputation and block the servers with poor IP reputation.

So, if the sender is blacklisted in Spamhaus, the mails from that sender may get rejected by the recipient mail server.

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4. Email filters specific to the recipient domain

In addition to server wide email filters and blocks, it is also possible to have custom email filters for each domain in a server.

At times, email rejection happens due to recipient-specific email filters or blacklists or security policies, even though there are no server-wide restrictions.

5. Blocks or filters in the sender mail server

While the error 571 is mostly due to blocks or rejections at recipient mail server, in certain cases, the sender mail server also can cause this error.

Some servers have outgoing firewalls or antivirus tools configured for controlling the traffic going out from them to certain recipients. These blocks or filters can also lead to email delivery failures.

If sender address is an external one that is not permitted to send mail to a distribution list, the mail would be rejected.

How to fix ‘571 Delivery not authorized message refused’ error in Exchange

In Exchange mail server, security restrictions for emails can be controlled with the use of connectors – sender and receiver.

While Send Connectors control the mails going out from the server, Receive Connectors control the incoming messages.

The error ‘571 Delivery Not Authorized Message Refused’ is commonly returned by an Exchange Server, if mails come to it from not-trusted senders.

To resolve this error, recipient mail server should configure their Receive Connectors and allow permissions on it for trust-worthy sender domains.

To add a new Receive Connector in Exchange, the steps are:

1. Open the Exchange Management Console. Choose the transport.

2. In the action pane, choose 'New Receive Connector'.

3. Create a new connector with type Internet.

4. On the Local network settings page, specify the mail server IP.

5. On the Remote network settings page, enter the IP address of the sender mail servers from which the connector is allowed to accept mails.

Once you allow the sender mail server to connect to your mail server via Receive connectors, the sender mails would be delivered fine without the bounce error ‘571 Delivery Not Authorized Message Refused’.

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In short..

Ensuring your mail server is not sending any spam, is crucial to avoid mail delivery failures for your sender domains.

Securing the mail server, periodic server audits, disabling malicious scripts, settings RDNS and SPF records, etc. are some of the security measures we adopt to prevent our servers from getting blacklisted.

There isn’t a one-fix-all solution for any error. Examining the mail logs, testing the email routing and checking the mail server settings are some ways we identify and fix the issue.

Bobcares also gives recommendations to server owners on how to secure their servers. If you’d like to know how to fix your mail server, we’d be happy to talk to you.