Category: Technical

Lets Encrypt Everything

Using SSL TLS to protect data in transit and authenticate servers you contacted originally required specialized software, complex configuration and expensive and complicated to require certificates. The need for specialized software is long since gone. Pretty much every web server and mail server will support SSL out of the box. Basic server configuration is now pretty simple […]


SPF debugging

Someone mentioned on a mailing list that mail “from” was being filed in the gmail spam folder, with the warning “Our systems couldn’t verify that this message was really sent by“. That warning means that Gmail thinks it may be phishing mail. Given they’re a well-known financial services organization, I’m sure there is a lot […]

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Trawling through the junk folder

As a break from writing unit tests this morning I took a few minutes to go through my junk folder, looking for false positives for mail delivered over the past six weeks. We don’t do any connection level rejection here, so any mail sent to me gets delivered somewhere. Anything that looks like malware gets […]

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DMARC News – Gmail p=reject and ARC announced this morning that Gmail will be moving to publishing a p=reject DMARC record in June of next year, much the same as Yahoo and AOL have. Unlike Yahoo and AOL, Gmail are giving those who will be affected plenty of time to prepare for any issues, and have waited until there are some potential ways […]

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IPv6 and authentication

I just saw a post over on the mailop mailing list where someone had been bitten by some of the IPv6 email issues I discussed a couple of months ago. They have dual-stack smarthosts – meaning that their smarthosts have both IPv4 and IPv6 addresses, and will choose one or the other to send mail over. […]

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On Friday I talked a bit about the history behind TXT records, their uses and abuses. But what’s in a TXT record? How is it used? When and where should you use them? Here’s what you get if you query for the TXT records for from a unix or OS X command line with dig […]


A brief history of TXT Records

When the Domain Name System was designed thirty years ago the concept behind it was pretty simple. It’s mostly just a distributed database that lets you map hostname / query-type pairs to values. If you want to know the IP address of, you look up {, A} and get back a couple of IP addresses. […]

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IPv6 Email is a little different

On Monday I talked about how big IPv6 address space is, and how many IPv6 addresses will be available to end users. We’re mostly an email blog, though, so what’s the relevance to sending email? If the recipient you’re sending to has an IPv6 mailserver you can send mail to them over IPv6, if you […]


IPv6 is big

IPv6 is big. Really big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist, but that’s just peanuts to IPv6. The old Internet, the one you’re probably using right now, runs on IP version 4. IPv4 addresses have […]


Microsoft Send

Microsoft Send is a new mail client by Microsoft for iPhones and soon Windows Phone and Android phones. Send is designed to send quick, short messages to contacts. Instead of building a chat application build on a proprietary protocol, Send sends and receives its messages over email and uses your existing mailbox to handle the […]

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  • Lost in the mists of time

    Over on the Farsight Security blog Joe St. Sauver talks about some of the early days of online abuse, on usenet. Laura and I were on the periphery of early usenet abuse, mostly as users, but Usenet (and IRC) around then were the places we both started with email abuse.No Comments

  • Ongoing Yahoo delays

    I've been hearing from folks over the last few days that they're seeing an uptick in deferrals from Yahoo! The deferrals are not uniform. ESPs report they're seeing some, but not all, customers affected. Other ESPs aren't seeing any changes. It's not just you. But it would be very worthwhile to dig into engagement and other stats. It's possible this is a new normal at Yahoo! and they're tightening filters to catch mail that doesn't fit their standards but was previously difficult to filter.No Comments

  • AOL starts using Sender Score Certification

    Good news for Sender Score Certified IPs. Return Path recently announced that AOL has joined the list of ISPs offering preferential treatment to certified IPs.  1 Comment