The return path determines where non-delivery reports (NDRs) or bounce notifications are sent when an email is unable to reach its intended recipient.
While the return path matching the sender address is acceptable for most common email practices, sending mail in bulk is one example of where a return-path envelope would differ from the sender address. In this case, the return path is used to park bounce notifications for further analysis after a particularly large email campaign.
The return path will not be visible to the recipient unless they view the original email headers. If the return-path differs from the sender address, the recipients will only see the sender address. It’s instead identified by mail servers communicating in the background.
To comply with industry standards, SMTP2GO migrated from SPF / DKIM verification to VERP in June 2019. VERP stands for Variable Envelope Return Path.
SMTP2GO now sends mail with a return-path email address at a subdomain of your sender domain name (Verified Senders). If a recipient domain is incapable of processing emails sent to it that use VERP, you can use the Maintaining the Return-path feature.
Previously, we would simply send emails using the exact same return-path email address as the one in your ‘From’ header. As the SPF protocol checks the domain name of the return-path email address, it will pass as there will be a CNAME pointing to us (and we maintain a correct SPF record at the subdomain it points to).
For more information about this, check out our blog post: Sender Domains Update.