Typically, a return path is an email address. It’s specified during the SMTP protocol communication process when emails are sent and received. In simple terms, the return path determines where the receiving mail server sends back it's bounced messages.
Variable Envelope Return Path or VERP is a useful technique which offers automatic detection and removal of undeliverable email addresses. It does this by using a different and unique return path for each recipient of a message.
What is VERP Used For?
VERP is generally used to process mail failures. Put simply, the hardest part of bounce processing is matching up a specific bounce message with the undeliverable email address that caused the bounce. VERP solves bounce processing issues by using a different return path for every email.
It does this by changing the sender address to include information about the original recipient of the email. So, for example, an email sent from to could use a sending address like business+joe= . Although this sending address also contains information about the original recipient, it's still a valid email address.
If the email delivery fails and it bounces back, the bounce message then comes back to that unique email address that also contains information about the recipient address. Ultimately, if a business sends out an email campaign to its email list, a VERP address will be generated for every recipient on the list.
This, in turn, means that, just by looking at the return addresses, it will be easy for the business to identify the addresses that caused the bounces.
In this way, it's easier to create a mailbox which allows the easily filtering of bounced email addresses. If the proportion of bounced messages is then too high, the address can be removed from the list.
Why Is VERP Important?
VERP is important because the use of a VERP address is an industry best practice which improves the deliverability of outbound messages to major mail providers like Yahoo, Hotmail, AOL, and Gmail.
It does this by providing more accurate details about each sending failure and it gives users a centralized location to view and access the information about all outbound messages.
With this information available, businesses can remove emails with a high proportion of bounces from their list. And if they remove these email addresses, they reduce their bounce rate. This, in turn, improves their email deliverability.
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