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Postini Likes DKIM Authentication

We've posted in the past how frustrating it can be to get legit email campaigns past the Postini firewall (see: Getting Blocked by Postini?). It just seemed very random how they filter emails. Why do some emails get through, and some don't?

We think we just stumbled upon the answer.

We'd recently been testing some DKIM authenticated MailChimp campaigns with our Inbox Inspector, just to see how things rendered. We were putting in gobbledy-gook placeholder text. I mean, sloppy junk that would normally get you spam filtered in a heartbeat. Our test campaigns were also very image-heavy, which is known to trigger spam filters. Here's a screenshot of how our test email looked in Outlook (just so you get an idea of how truly bad our test email was):


Lo and behold, they all got past Postini with flying colors.


Normally, you'd want way more text in the message to "balance out" the big header graphic. It also helps if you don't use a bunch of random junk text. But DKIM authentication seemed to tip the scales and got our message through.

We still scored high on the content filters (2.0 Spam Assassin Score), so I'm sure that without a properly configured email server, even DKIM wouldn't be a silver bullet to get past Postini. But boy, it sure seems to help.

An interesting side note: In addition to the fact that our email was too image-heavy, almost every spam filter penalized us for having "fda" in our email (as in, "This drug has been approved by the FDA to enlarge..."). One more example how "every word in the English dictionary is now a spam word" (as someone at ReturnPath told us recently) and how you need to be careful if you're sending test campaigns with placeholder text in it.

MailChimp users, you will soon have the option of adding DKIM authentication to your accounts with the click of a button. Look for an announcement soon.

Learn more about our Inbox Inspector add-on

Learn more about DKIM authentication

July 2, 2007 in Deliverability | Permalink | Comments (0) | TrackBack

Tiny Fonts Trigger Spam Filters

One of our users just designed a nice email campaign for his client, and tested it in our Inbox Inspector. Overall, he received a passing score, but we noticed something in the spam filter checker.

Spam Assassin and MessageLabs didn't like the fact that his email footer used "tiny fonts" in it:


As you can see, Spam Assassin gave it a full 2.6 points for that! They say the default threshold for Spam Assassin is "5" but we tell people to try to stay below "3" (because c'mon---who really keeps their threshold at 5 these days?). Better safe than sorry.

Our customer really had a nice looking template, and wasn't trying to hide anything. But spam filters think that tiny fonts are a sign that some spammer is trying to embed a whole bunch of confusing content into their message to throw off their scent.

Our customer's footer had text specified with: "font-size:9px." Interestingly, our own email templates specify our font size to be 10px, but we've never been flagged for that.

So if you have fonts in your footer that are really, really small (like we all tend to do), make sure they're no smaller than 10px in size.


See what else Spam Assassin scans for in your email.

Learn how you can use MailChimp's Inbox Inspector to test your email marketing campaigns and transactional emails

June 6, 2007 in Deliverability, Tips, Tricks, Best Practices | Permalink | Comments (1) | TrackBack

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