How does SPF/DKIM "auto authentication" work on mail chimp?

Question

Mail chimp offers three levels of authentication when doing email campaigns.

1. Manual Authentication
2. No Authentication
3. Auto Authentication

From what I understand Manual Authentication is when you set up your own SPF/DKIM records on your DNS.

No Authentication is when no body sets up anything, and I'm pretty sure deliverability goes way down.

The Auto Authentication is what I am curious about. All they do is require the person sending the email to approve that their email address is ok to send from with a validation email. I'm done research, and I can't figure out how mail chimp and other people do this auto-authentication.

Is there any service out there, or would we have to set up our own email servers to accomplish something like this.

Also what kind of effect on deliverability is the "auto" authentication.

Answer 1

Mailchimp is able to automatically attach authentication to your email campaigns without you setting up explicit approval on your server because if you look at the headers of the email when you send it, they are never really affiliating with your server. It will appear as though your campaign was sent from:

[email protected]  

But if you look closely at the headers of the email you will find something similar to FROM:

From: [email protected] 

And the sender will say something like:

[email protected]

So all of the authentication is set up by Mailchimp on Mailchimp's own outbound SMTP servers, there is never really any interaction with your server.. yoursite.com.

Further:

• Mailchimp - Email Delivery for IT Professionals
• Mandrill API Documentation - Subaccounts