Our Email Delivery Manager, Kiersti Esparza, has written a few blog posts about how we get your email into your recipient’s inbox. From the time you click “launch”, there’s a ton of hard work and a little magic that happens. So let’s have a look at Part 1 which focus on Authentication, Reputation, Feedback Loops and Bounced Email.


When you send a high volume of email it is very important that you build a great sending reputation with Internet Service Providers (Hotmail, Yahoo, AOL, & Comcast to name a few). How do you do this? You send email to recipients that WANT it, and you use industry protocols that ISPs require when they screen incoming email to their users. VerticalResponse implements all of the proper Authentication mechanisms required to do this.


Because we use these authentication mechanisms we have built a good sending reputation over time and we’re able to get great inbox delivery rates. Third party monitoring shows that we average above a 98% inbox delivery rate. If we didn’t use these 4 authentication mechanisms we would not be considered a ‘trusted sender’ when we attempt to deliver email and could easily be blocked or the email directed to the bulk folder. Authentication is in place to enable us to build a good sending reputation, and to ensure that we are identifying ourselves accurately in the “From Address”.

Feedback Loops  

A Feedback Loop is a partnership with an Internet Service Provider so that when a recipient complains about a piece of email by clicking the SPAM or BULK button in their email reader, we automatically receive that complaint back and unsubscribe them from your email list. This protects the health of our sending network and ensures your lists don’t contain recipients who no longer want to receive your mailings.

The Cause of a Bounce

A bounce occurs when an email can’t be delivered at that particular time. There are two types of bounces; hard and soft. With VerticalResponse soft bounced emails are retried for up to 3 days. The VAST majority of soft bounces are delivered within this window. On the unlikely chance that a soft bounce delivery problem remains, that address will remain valid for future mailings.

Hard bounces, such as bounces indicating that the address is not valid, generally bounce within the first couple hours of a campaign launch and are marked bounced in your reporting dashboard. These addresses are unavailable to mail in later campaigns.

Bounces and unsubscribes are the reason that your email marketing lists can shrink over time if you are not actively growing them. Some report the average attrition rate to be 20 – 30% annually due to people changing jobs, changing email addresses, unsubscribing, etc.

We do not process out of office responses or auto-responses as bounces, our system ignores a majority of these messages. When an auto response is received, such as an out of office reply, it is an acknowledgment that the mail has been delivered, though likely will be read at a later time. We monitor our bounces to ensure that we are catching all of the possible out of office reminders so they are not improperly categorized as hard bounces.

Email delivery is a pretty interesting topic with quite a few categories. Up next we will cover Email Rendering and Understanding Email Response Rates.

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