Variable Envelope Return Path (VERP) - SMTP Mail From Field

The use of a VERP address is an industry standard practice and improves the deliverability of outbound messages to major email service providers.

Return Path

Email messages contain two "from" addresses, the Return Path and the Friendly From address.

  • The Return Path address is also known as the Mail From, Envelope From, 5321.from, or the Bounce address. This address is not shown to the recipient. It is  an email address specified during the SMTP protocol communication process that determines where the receiving mail server sends back its bounce messages.
  • The Friendly From address is also known as the Display From or 5322.from. This is the address that is shown to a recipient.

Variable Envelope Return Path: Overview

A Variable Envelope Return Path, or VERP, address, is a custom return path address that allows SocketLabs to capture, analyze, process, and report upon bounces for any outbound mail sent on our platform. We encode unique data about each outbound message into an address, and will use that in the MAIL FROM protocol command.

An example of a VERP address is:

Benefits of VERP Addresses

The use of a Variable Envelope Return Path allows the SocketLabs On-Demand platform to better interpret message failures and provide more accurate details about each failure individually. It also allows for us to provide a single centralized location to view and access the information about all outbound messages processed through the account.

Additionally, the use of a VERP address enables SocketLabs to ensure that all outbound messages delivered through our network pass SPF authentication checks at their delivery point. 

Disabling VERP Encoding

SocketLabs does not disable the use of a VERP address across an entire account or server. If VERP is causing issues in the delivery process of your mail we may disable its use for a specific domain, please contact our Support team for more information.

Is There Anything Else I Should Know?

If you are concerned about no longer receiving bounce messages to your own addresses, please see: How SocketLabs Handles Non-Delivery Reports & Bounces.

E-Fax services often authenticate messages using SPF and the return path address. Users may experience issues sending outbound e-fax messages through SocketLabs and should contact support to ensure VERP is disabled to your e-fax service provider's domain.

When messages are sent without a Friendly From Address field in the message headers, receiving email systems may choose to insert the VERP address as the From Address field visible to recipients. If you are experiencing this issue, ensure that your messages include a properly formatted From field within the message headers.