SenderID is dead

A question came up on the email geeks slack channel (Join Here) about SenderID. They recently had a customer ask for SenderID authentication.

We’ve written about it a few times: (Hotmail moves to SPF Authentication and Until it stops moving) but we’ve not actually stated the reasons why in a post.

SenderID was basically SPF version 2. It tried to use the same mechanism as SPF to authenticate the visible from address. In some ways it was a predecessor to DMARC. It was an authentication method championed by Microsoft.

The really important thing to remember is that Hotmail was the only domain that really used SenderID. It was a check built into some versions of Exchange servers, too. But it was never really used outside of Microsoft.

In 2012, the IETF published an informational RFC that looked at deployment of SPF and Sender ID. The author looked at a number of different things and concluded there wasn’t much use of Sender ID.

The absence of significant adoption of the [SUBMITTER] extension, SENDER-ID], and [PRA], indicates that there is not a strong community deploying and using these protocols.

Six months after that RFC was published, Microsoft announced they were moving away from Sender ID. Given they were the only major implementation, this was the signal that it was a dead authentication method.

There is no reason to publish Sender ID records. It’s dead.

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July 2016: The Month in Email

We got to slow down — and even take a brief vacation — in July, but we still managed to do a bit of blogging here and there, which I’ll recap below in case you missed anything.
Sonoma1
At the beginning of the month, I wrote about email address harvesting from LinkedIn. As you might imagine, I’m not a fan. A permissioned relationship on social media does not equate to permission to email. Check out the post for more on mailing social media contacts.
Even people who are collecting addresses responsibly can face challenges. One of the most important challenges to address is paying attention to your existing subscription processes, testing them regularly, evaluating effectiveness and optimizing as needed.
Our most commented-upon post this month was a pointer to a smart writeup about Hillary Clinton’s email server issues. Commenters were pretty evenly split between those who agreed that they see this kind of workaround frequently, and those who felt like regulatory processes do a good job managing against this kind of “shadow IT” behavior. I wrote a followup post on why we see this kind of workaround frequently in email environments, even in regulated industries, and some trends we’re seeing as things improve.
In other election-related email news, we saw the challenges of campaign email being flagged as spam. As I pointed out, this happens to all campaigns, and is nothing unique to the Trump campaign. Still, there are important lessons for marketers here, too, in terms of list management, email content, frequency, and engagement — all of which are inextricably linked to deliverability.
Speaking of spam and engagement, Steve took a look at some clickthrough tracking revealed through a recent spam message I received — and why legitimate marketers should avoid using these sorts of URL referrers.
On the topic of authentication, I wrote a quick post about how seeing ?all in the SPF record tells me one thing: the person managing the record isn’t doing things properly. Need a refresher on authentication? Our most-read blog post of all time can help you out.
And as always, send me your interesting questions and I’ll be happy to consider them as I resume my Ask Laura column in August.

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Are they using DKIM?

It’s easy to tell if a domain is using SPF – look up the TXT record for the domain and see if any of them begin with “v=spf1”. If one does, they’re using SPF. If none do, they’re not. (If more than one does? They’re publishing invalid SPF.)
AOL are publishing SPF. Geocities aren’t.
For DKIM it’s harder, as a DKIM key isn’t published at a well-known place in DNS. Instead, each signed email includes a “selector” and you look up a record by combining that selector with the fixed string “._domainkey.” and the domain.
If you have DKIM-signed mail from them then you can find the selector (s=) in the DKIM-Signature header and look up the key. For example, Amazon are using a selector of “taugkdi5ljtmsua4uibbmo5mda3r2q3v”, so I can look up TXT records for “taugkdi5ljtmsua4uibbmo5mda3r2q3v._domainkey.amazon.com“, see that there’s a TXT record returned and know there’s a DKIM key.
That’s a particularly obscure selector, probably one they’re using to track DKIM lookups to the user the mail was sent to, but even if a company is using a selector like “jun2016” you’re unlikely to be able to guess it.
But there’s a detail in the DNS spec that says that if a hostname exists, meaning it’s in DNS, then all the hostnames “above” it in the DNS tree also exist (even if there are no DNS records for them). So if anything,_domainkey.example.com exists in DNS, so does _domainkey.example.com. And, conversely, if _domainkey.example.com doesn’t exist, no subdomain of it exists either.
What does it mean for a hostname to exist in DNS? That’s defined by the two most common responses you get to a DNS query.
One is “NOERROR” – it means that the hostname you asked about exists, even if there are no resource records returned for the particular record type you asked about.
The other is “NXDOMAIN” – it means that the hostname you asked about doesn’t exist, for any record type.
So if you look up _domainkey.aol.com you’ll see a “NOERROR” response, and know that AOL have published DKIM public keys and so are probably using DKIM.
(This is where Steve tries to find a domain that isn’t publishing DKIM keys … Ah! Al’s blog!)
If you look up _domainkey.spamresource.com you’ll see an “NXDOMAIN” response, so you know Al isn’t publishing any DKIM public keys, so isn’t sending any DKIM signed mail using that domain.
This isn’t 100% reliable, unfortunately. Some nameservers will (wrongly) return an NXDOMAIN even if there are subdomains, so you might sometimes get an NXDOMAIN even for a domain that is publishing DKIM. shrug
Sometimes you’ll see an actual TXT record in response – e.g. Yahoo or EBay – that’s detritus left over from the days of DomainKeys, a DomainKeys policy record, and it means nothing today.

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Gmail showing authentication results to endusers

A bit of older news, but worth a blog post. Early in August, Gmail announced changes to the inbox on both the web interface and the android client. They will be pushing authentication results into the interface, so end users can see which emails are authenticated.

These are not deliverability changes, the presence or absence of authentication will not affect inbox delivery. And the gmail Gmail support pages clarify that lack of authentication is not a sign that mail is spam.
This isn’t a huge change for most ESPs and most senders. In fact, Gmail has reported more than 95% of their mail is authenticated with either SPF or DKIM. Now, Gmail does a “best guess” SPF – if it looks like an IP should be authorized to send mail for a domain (like the sending IP is the same as the MX) then it’s considered authenticated.
It’s good to see authentication information being passed to the end user.

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