What Is a Return-Path Address?

A Return-Path is the designated email address where bounced messages and other email feedback are sent. So, if an outbound email can’t be delivered, it’ll end up at the Return-Path, which is specified by the Return-Path header in an email and invisible to other parties. In addition to the Return-Path moniker, there are several variants of the name, including bounce address, reverse path, envelope from, envelope sender, return address, and MAIL FROM. (For this write-up, we’ll stick with Return-Path.)

How Does the Return-Path Apply to SPF?

With regard to SPF, the Return-Path (in addition to being the email address that recipient email servers use to notify the sender of delivery problems (bounces)) is the address that the email server uses to get an SPF Record (TXT DNS record). When it retrieves the record, the record will contain a list of approved IP addresses that are allowed to send email for the domain part of the Return-Path address. The recipient email server will take that list and compare it to the IP address that sent the message. If it matches, the email will pass SPF authentication. If it fails, the message is indicative of spam.

Return-Path and SPF Alignment

The return path also becomes critical to passing the SPF Alignment test. This test is part of DMARC, where by a message must either pass both SPF Authentication and Alignment tests or pass both DKIM Authentication and Alignment tests to be considered DMARC Compliant. Now what does that mean? Basically, it means that the domain present in the Return-Path must match the domain found in the FROM address (the one you will see in a inbox when reading an email).

Why Set a Custom Return-Path?

Although a custom Return-Path isn’t required, it has many advantages. Moreover, if you have a DMARC policy implemented for your domain, setting up a custom Return-Path to achieve SPF alignment is strongly advised. DMARC checks the Return-Path of a message to confirm that domain matches the domain in your “From” address. If the path doesn’t match your “From” address, those emails will fail DMARC’s SPF alignment authentication.

For instance, if your company sends email from address.com, you can still pass SPF and DKIM authentication; however, because the Return-Path and “From” addresses aren’t using the same domain, SPF won’t pass for DMARC verification. When the Return-Path domain mxbounces.address.com is set up and emails are sent from address.com, the domains are aligned for DMARC to operate. This custom Return-Path scenario would create the header <mx_bounces@mxbounces.address.com>. Note: Depending on your business’s email provider, the custom Return-Path will vary.

Further Custom Return-Path Intel

To set up a bounce domain, establishing a CNAME record with your chosen DNS service provider is required. Once available, the custom bounce domain will override the default Return-Path value of address.com for all your outbound messages. By customizing your Return-Path, the ability to present your customer emails in a more professional manner (i.e., removes the default third-party “on behalf of” designation) is attained. Also, it improves overall deliverability of your messages to inboxes rather than junk/spam folders.

Summation

Typically, all email errors referring to bounced emails are sent back to the sender’s email address, which can be overwhelming and quite annoying. By implementing a custom Return-Path, you’ll be able to manage bounces more efficiently because the aforementioned error messages won’t be lumped together with legitimate emails in the same account. If your business relies on email to communicate with current and future clientele, a custom Return-Path will greatly benefit your campaigns.