Delivery Status Notifications

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Delivery Status Notifications

Post by RollerNetSupport »

The following message was sent by email to accounts with a contact preference of "System notices only" or "You can contact me" on February 18, 2009.

[rollernet] Delivery Status Notifications

* * This message is being sent to "system notice" contacts because it describes an operational change in our services. If this is the first time you are receiving a message from us do not be alarmed; our announcement lists are extremely low traffic. * *

Effective February 18, 2009 the Roller Network mail services will no longer request a delivery status notification (DSN) to be generated by default. These messages are commonly seen as "bounce" notices. We believe sending bounces to possibly forged return addresses is not proper behavior for a mail service provider like ourselves. We're not here to create more problems for others to deal with. These DSN messages are the prime cause of backscatter - a phenomenon we seek to prevent.

The good news is this change lets us turn off the bounce and backscatter scanner. (It's described under the backscatter prevention policy.) This scanner would temporarily disable a mail domain if a bounce was detected to prevent a DSN from being generated by further errors. It's the cause of those "Mail Error Detected" messages. Hopefully you'll find the removal of the bounce scanner a welcome change.

This change does violate the spirit of RFC 2821 section 3.7 which states that if an SMTP server has accepted a message for delivery but later finds the message cannot be delivered, it must construct an "undeliverable mail" notification and send it to the originator as indicated by the reverse-path. Unfortunately, when 2821 was written it did not consider mail filtering, spam, and the forgery attempts that dominates modern email systems. It is through our operational experience that we believe blindly sending delivery status notifications does more harm than good. However, we are making this change in an RFC complaint manner; with RFC 1891 section 5.1, the NOTIFY parameter.

Roller Network provides multiple mechanisms that notify or allow you to view the delivery status of messages destined for your mail server: mail logs and service alerts. Through the mail logs you can view the delivery status attempt between our servers and yours. The service alerts feature allows our mail system to send alerts to a pager or other email address when a "deferred" or "bounced" delivery condition is detected.

If you have any questions, please let us know.

Roller Network isn't the first company to make this type of change. We believe we're second after DynDNS's MailHop service. The difference between our implementation and theirs is that we're using the NOTIFY extension to control DSN generation rather than discarding messages. With ours, a sender can still re-enable DSN if they choose.

This change does not modify the behavior of our mail servers (running Postfix); we are simply using the NOTIFY parameter of the ESMTP RCPT command as defined in RFC 1891 section 5.1. Specifically, we're appending "NOTIFY=NEVER" to the RCPT TO command unless an existing NOTIFY was already specified. This means you or the original sender can still turn delivery status notifications back on if you include the appropriate NOTIFY parameter with the RCPT command. When "NOTIFY=NEVER" is specified Postfix will not generate a delivery status notification.

For more information on Postfix DSN support see:
For more information on backscatter see:
Technical Support
Roller Network LLC