Internet and Web Services

A Division of
Electrosonics, Inc.

-  Home 
Contact Us 


-  Services
-  Website Hosting
-  Website Design

Frequently Asked Questions

  1. When I send email, your server reject it with the follow message: "This server requires PTR for unauthenticated connections"

When I send email, your server reject it with the follow message: "This server requires PTR for unauthenticated connections"

When your company sends email, it bounces as undeliverable. The error message sent by our server to your server upon attempted mail delivery is as follows:

This server requires PTR for unauthenticated connections

What this message means is that your dedicated email server is lacking a reverse DNS (rDNS) entry in your DNS settings. You will need to contact your DNS hosting company and request that they insert a reverse DNS record (also called a PTR record) for the IP address of your email server. The PTR record should be the FQDN (Fully Qualified Domain Name) of your mail server. The FQDN of your mail server should match the MX record DNS entry. The reverse PTR DNS entry should list your FQDN. Also the SMTP response greeting to SMTP connections to and from your SMTP server needs to respond with the FQDN.

Internet standards dictate these requirements. RFC1912 2.1 says you should have a reverse DNS for all your mail servers. It is strongly urged that you have them, as many mail servers will not accept mail from mail servers with no reverse DNS entry. Internet standards also dictate that the SMTP response greeting should reply with your FQDN. Many mail servers will verify that the IP address your are coming from (rDNS) matches the FQDN in the SMTP response header. Lack of a match is a strong indicator of a spammer and may also be a cause for email delivery failure.

A very nice tool to check all these settings can be found here:


If you you are using the default SMTP service in a Windows 2000 or Windows 2003 server environment, you may be able to change the SMTP greeting (HELO Response) to respond with your FQDN. To resolve the SMTP greeting issue, please review the SMTP server settings (found on the IIS service MMC or within the Exchange connectors). Right click on the SMTP server and click on properties, click on the delivery tab, click the Advanced... button and fill in the FQDN field with your fully qualified domain name.

You may need to stop and start the SMTP service for the change to become active. Once you have made the change to the SMTP service, run the DNS report for your domain to verify that the mail server host name in the greeting is correct.

Your DNS hosting company should be able to advise you on the procedure to follow to update your DNS records and set up the reverse DNS PTR record. Changes in the DNS records by your DNS hosting company may take 12 to 48 hours to become effective. Your DNS hosting company should be able to let you know more specifically when you can expect the update to the rDNS to become available.

Send email to webmaster@m80.net, with questions or comments about this web site.
Call us at 586-415-5555 or 800-858-8448, with questions about our company or to place an order.
1997-20011, 2012 Electrosonics, Inc., Fraser, Michigan
M80.net is an Internet Services division of Electrosonics, Inc.

This page was last updated on: February 23, 2002

Back to Top

Hit Counter