How the return path works
The return path, also known as the reverse path, works by setting the return path header to direct bounced messages to your secondary email to process bounces. When you have messages that can't be delivered, you want to know the reason why in order to determine if a new sender's email address is available. A custom return path address is often set up by a developer and is different from your sending address.
Once a mailbox provider receives your email, your identity will be validated. In this process, your sending reputation is also evaluated by the email program. If your email is deemed spam or trash, it will not reach its intended destination. Without the return path header in place, you won't know that your email went to the spam folder and wasn't delivered.
The return path header helps you by providing a return path domain that is the same domain as your main email address.
Consider the two types of email issues that will cause a bounce: a soft bounce or a hard bounce. When you have a hard bounce, something is wrong with the email address itself. The email address can be non-existent, or you may have typed in the address incorrectly. This is an issue that can be fixed by typing the address again, or the email address may no longer be viable.
A soft bounce is usually a temporary problem. In this case, the destination inbox could be full, the attachment size might be too large, or the attachments may not work.
If your email hard bounces, all you can do is make sure the email address was typed in correctly. If the address is correct, remove it from your list because it is no longer viable. If you continue to send out emails that are not deliverable, this will lead to bigger problems with deliverability over time because it will impact your sender reputation.
An email that soft bounces should be monitored to see if it bounces a second time. This can occur if the destination inbox is full or if there is an issue with the mailbox provider. If an email bounces more than once, this should be treated like a hard bounce and taken off your mailing list.
Why is the return path important in email marketing?
As a business with a large mailing list, you need to be sure that your email return path is set up. If you don't set up a return path address, you can end up with hundreds of bounced emails in your primary inbox. It's often not a fault on your end when an email bounces, but your reputation to email service providers will decrease the higher your bounce rate becomes.
Once you have a return path address set up that isn't the sender's email, every bounced message will go to the email return path instead. You will be able to process these messages better and can keep them separate from the active, functioning emails you have sent out to potential customers.
As the SMTP address is a return path, this will improve your deliverability and sending reputation. This makes it easier for the recipient's email provider to determine if you are sending spam and improves your ability to get your message through spam filters.
The emails you send will have more credibility, and your sending reputation will improve as you succeed at getting messages through to the intended inbox.