Monthly Archives: May 2014

DKIM Key Rotation

Several people have asked me about how to rotate DKIM keys in the past few days (as if you’re modifying anything to mitigate replay attacks, you need to invalidate the signatures of all the mail you sent before you made those changes).    [icon name=”key” class=”2x spin”] You really, really should be rotating your DKIM keys […]


DKIM and injected headers

If you look at the DKIM-Signature header in any piece of email signed with DKIM you’ll see that one of the fields it contains, the h= field, lists some email header names, for example: h=From:Subject:Date:To:MIME-Version:Content-Type Those are the headers that were signed when the mail was sent, and they’re the only headers that will be checked […]


DKIM replay attacks

Replay attacks on DKIM signed messages When you receive an email validly signed with DKIM by that might not mean that sent the email to you, or that they even sent this email at all. What it does tell you is that at some point in the past, signed an email with exactly the […]


Spot the unsub

A new game! Spot the unsub! Our first challenge is the footer from a major software company. How long does it take for you to to find the unsub link?   What’s even more annoying is that I never actually subscribed to mail from this company. A few years ago I was doing some work […]


The more things change

I was doing some research about the evolution of the this-is-spam button for a blog article. In the middle of it, I found an old NY Times report about spam from 2003. At the same time, the argument is intensifying over what represents legitimate e-mail, particularly when it ends up being blocked by an antispam […]

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Yahoo FBL problems

Multiple ESPs are reporting that the volume of Yahoo! FBL reports have slowed to a trickle over the last 24 or so hours. While we don’t know exactly what is going on yet, or if it’s on track for being fixed, there does seem to be a problem. There has been some ongoing maintenance issues […]


Email templates using Grunt

A Grunt workflow for designing and testing HTML email templates with SCSS.

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It's about the spam

Tell someone they have hit a spamtrap and they go through a typical reaction cycle. Denial: I didn’t hit a trap! I only send opt-in mail. There must be some mistake. I’m a legitimate company, not a spammer! Anger: What do you mean that I can’t send mail until I’ve fixed the problem? There is no problem! You can’t […]

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Emoji – older than you think

It might just be random 17th Century punctuation, but this poem from 1648 certainly seems to be using a smiley face emoji. (OK, it’s probably not intentional, but it’s lovely intersection of the emoji and the word.)

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TLS and Encryption

Yesterday I talked about STARTTLS deployment, and how it was a good thing to support to help protect the privacy of your recipients. STARTTLS is just one aspect of protecting email from eavesdropping; encrypting traffic as the mail is being sent or read and encrypting the message itself using PGP or S/MIME are others. This table […]


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