February 28th, 2011

VERP now supported for High Volume Bounce Analysis

LuxSci’s High Volume Outbound Email service now supports the optional use of VERP / Variable Envelope Return Path for simplified bounce message analysis.

Normally, when an email message is sent, but fails to reach its destination, a “bounce message” is sent back to the “Envelope Sender” (i.e. the “Return path” address, which may or may not be the same as the “From” address).  These bounces inform senders of delivery issues and allow for the management and pruning of mailing lists.  However, there is no uniformity in the format of these bounces messages.  It is even sometimes the case that it is not possible to tell to whom the message was originally sent!  This makes analysis of bounces both difficult (no standard format) and imperfect (can’t always tell).

Enter VERP – “Variable Envelope Return Path”

With this method of sending, the address to which bounces messages are sent (the Return Path) is customized for every recipient, so that it contains the failed address.

For example, lets say the message is From “newsletters@newsdomain.com” and To “somebody@luxsci.net”.  With VERP enabled, the bounces will be sent to the address “newsletters+somebody=luxsci.net@newsdomain.com”.

Most mail servers will deliver these “plussed” addresses to the mailbox of “newsletters@newsdomain.com”.  There, automated processes can look at the “To” addresses for the messages to (1) identify which are bounces, and (2) easily identify what addresses failed.

Use of this encoding scheme for the bounce messages solves the problems of bounce message uniformity and determination of what address failed. All you need are:

  • A return address that supports “plussed addressing” for delivery of these bounces
  • A program to read these messages and prune your mailing list (or you could do this manually if your list is small).

And Without VERP?

Without VERP, all of the bounce messages go back to a single return address.  To determine what addresses bounced (and why), one needs to parse the message content of these to determine (or guess) what happened.

LuxSci also provides  a service to High Volume accounts where by we auto-download bounce messages from a POP email box, parse these messages, and send the customer a list of failed addresses.  This is not quite as reliable as VERP, but works for any sending pattern.

How to Enable VERP?

High Volume customers can enable VERP sending on a per-user basis in the “Email Tools > Outbound Email > Copies of Messages” area of their user settings.  Note that use of VERP, like that of anonymized outbound email, will require use of a special SMTP port.

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