Ask Laura: Confused about Authentication

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Dear Laura,
I have a client moving from an external ESP to an internal system. They send approximately eight million messages per year, and these are primarily survey emails on behalf of their clients.
We’ve had some conversations about authentication, and I’m trying to help them figure out if they just need DMARC or if they also need DKIM and SPF. It seems some ISPs prefer different methods, and I’m not sure what to advise them.
Help!
Authentically Confused


Dear Authentically Confused,
The different technologies authenticate different things.
DKIM authenticates the email and ties the reputation in the d= value. We recommend DKIM to all our clients.
SPF authenticates the Envelope From/Return Path/5321.from value (and sometimes the HELO/EHLO value). We recommend SPF to all our clients.
DMARC uses DKIM and/or SPF authentication to authenticate the value in the visible from address (5322.from). DMARC requires that the d= value or the SPF value are in the same “organizational domain” as the visible from address (there is more about this in my DMARC primer post A brief DMARC primer). Once you can authenticate the visible from address, there are two things DMARC does for you. The first is a reporting scheme where you can get reports every time one of your email messages fails SPF or DKIM authentication. The second is a policy process where you ask receiving ISPs to implement a particular policy when the authentication fails (quarantine or reject).
We recommend clients monitor mail for at least 6 months before publishing a p=reject policy so you have a clear understanding of what mail will fail. Publishing a p=reject policy will cause valid mail that you send to fail in some tiny percentage of cases. For some senders this is a reasonable policy decision and should be implemented. For some senders this mail is too important to be rejected for authentication failures.
To summarize, we do recommend DKIM and SPF for all of our clients. There are some free tools on our site you might find helpful. It does not seem like DMARC would be useful for your client right now, since the emails they are sending are not transactional in nature or important account information that would be problematic if rejected.
Feel free to reach out if we can help you with more specific issues related to authentication.
Laura


Confused about delivery in general? Trying to keep up on changing policies and terminology? Need some Email 101 basics? This is the place to ask. We can’t answer specific questions about your server configuration or look at your message structure for the column (please get in touch if you’d like our help with more technical or forensic investigations!), but we’d love to answer your questions about how email works, trends in the industry, or the joys and challenges of cohabiting with felines.
Your pal,
Laura

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What to expect in 2016

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This year, though, I do see changes for everyone in the email space. Most of them center on finally having to deal with the technical debt that’s been accumulating over the past few years. I see ISPs and ESPs spending a lot of development effort to cope with the ongoing evolution authentication requirements.
When people started seriously looking at how to authenticate email, the first goal was getting organizations to implement the protocols. This was a practical concession; in order for a new protocol to be used it needs to be widely implemented. Phase one of authenticating email was simply about publishing protocols and getting organizations to use them.
During phase one, the organization that authenticated a mail hasn’t been important. In fact, the SPF spec almost guarantees that the ESP domain is the authenticated domain. In DKIM, the spec says any domain could sign as long as they could publish a public key in that domain’s domainkeys record.
ESPs took full advantage of this and lowered their own development overhead by taking most of the authentication responsibility on themselves. Their domains were in the 5321.from and they published the SPF records. Domains they control were in the d= and they generated and published the DKIM keys. Mail was authenticated without ESP customers having to do much.
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We’re now entering phase two, and that changes thing. In phase two, SPF and DKIM are used as the foundation for user visible authentication. Neither SPF nor DKIM were designed to be user visible protocols. To understand what they’re authenticating you have to understand SMTP and email. Even now there are days when I begin talking about one of them and have to take a step back and think hard about what is being authenticated. And I use these things every day!
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Prior to DMARC no one really paid much attention to the domain doing the authentication. Authentication was a yes or a no question. If the answer was yes, then receivers could use the authenticated domain to build a reputation. But they weren’t really checking much in the way of who was doing the authentication.
In the push to deploy authentication, ESPs assumed the responsibility for authentication deployed ESPs took the responsibility and did most of the work. For many or most customers, authentication was as simple as clicking a checkbox during deployment. Some ESPs do currently let customers authenticate the mail themselves, but there’s enough overhead in getting that deployed that they often charged extra to cover the costs.
DMARC is rapidly becoming an expectation or even a full on requirement for inbox delivery. In order to authenticate with DMARC, the authenticating domain must be in the same domain space as the visible from. If senders want to use their own domain in the visible from, DNS records have to be present in that domain space. Whether it’s a SPF TXT record or a domainkeys record the email sender customer needs to publish the correct information in DNS. Even now, if you try to authenticate with DKIM through google apps, they require you to publish DNS records.
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Getting DNS updates through some big companies is sometimes more difficult than it should be. I had one client a few years ago where getting rDNS changed to something non-generic took over a month. From an IT standpoint, changing DNS should require approvals and proper channels. Marketers may find this new process challenging.
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In 2016 a lot of companies will discover their current infrastructure can’t cope with modern authentication requirements. A lot of effort, both in terms of product development and software development, will need to be spent to meet current needs. This means a lot of user visible features will be displaced while the technical debt is paid.
These changes will improve the security and safety of email for everyone. It won’t be very user visible, which will give the impression this was a slow year for email development. Don’t let that fool you, this will be a pivotal year in email.

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When I got to my real mail client I checked headers, and sure enough, it wasn’t really from Pizza Hut. I’m guessing actually malware, but I don’t have a forensics machine to click the link and I’m not doing it on anything I can’t wipe (and have isolated from the rest of my network).
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