Can we put the FREE!!! Myth to bed?

Really. Single words in the subject line don’t hurt your delivery, despite many, many, many blog posts out there saying they do. Filters just don’t work that way. They maybe, sorta, kinda used to, but we’ve gotten way past that now.
In fact, I can prove it. Recently I received an email from Blizzard. The subject line:
Laura — Last Chance to Claim Your FREE Copy of Warlords of Draenor — Including Level 90 Boost! Offer Expires Monday! Last Chance to Claim Your FREE Copy of Warlords of Draenor — Including Level 90 Boost! Offer Ends Monday!
We have an email with

… two instances of FREE in all caps

… 4 different exclamation points

… Offer Expires

… Last Chance

… Unsubscribe

all right there in the subject line.
And what does Spamassassin say about the mail?

X-Spam-Flag: NO
X-Spam-Status: No, score=-7.193 tagged_above=-999
required=6.31 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1,
DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1,
HTML_IMAGE_RATIO_04=0.556, HTML_MESSAGE=0.001,
RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H3=-0.01,
RCVD_IN_MSPIKE_WL=-0.01, RCVD_IN_RP_SAFE=-2,
RP_MATCHES_RCVD=-1.428, SPF_HELO_PASS=-0.001,
SPF_PASS=-0.001] autolearn=ham
autolearn_force=no

See that first line? X-Spam-Flag: NO
See the next line: score=-7.193. Notice the negative? That’s almost 14 points less than what is needed for our installation of SpamAssassin to mark a message as spam.
Words in the subject line are not used for filtering in any sane filter.
Exclamation marks don’t trigger filters. 
FREE does not trigger filters. 
It’s time to retire the myth that spam filters pay any special attention to the subject line. They don’t. In fact, to a mail server the Subject line is just another bit of content. One that is only special because it starts with a defined field name (Subject), has a colon and contains a line terminated by CRLF. In fact, a subject line isn’t required for an email.

The only required header fields are the origination date field and the originator address field(s). All other header fields are syntactically optional. More information is contained in the table following this definition. Section 3.6, RFC5322

Section 3.6, RFC5322

Filters don’t treat the subject line any differently than the rest of the email content.
(For the Horde.)

Necessary but not sufficient
Memories of Spam in May

Related Posts

Dodging filters makes for effective spamming

Spam is still 80 – 90% of global email volume, depending on which study look at. Most of that spam doesn’t make it to the inbox; ISPs reject a lot of it during the SMTP transaction and put much of rest of it in the bulk folder. But as the volumes of spam have grown, ISPs and filters are relying more and more on automation. Gone are the days when a team of people could manually review spam and tune filters. There’s just too much of it out there for it to be cost effective to manually review filters.
In some ways, though, automatic filters are easier to avoid than manual filters. Take a spam that I received at multiple addresses today. It’s an advertisement for lists to “meet my marketing needs.” I started out looking at this mail to walk readers through all of the reasons I distrusted this mail. But some testing, the same sorts of testing I do for client mails, told me that this mail was making it to the inbox at major ISPs.
What told me this mail was spam? Let’s look at the evidence.
listsellingspam_thumb

Read More

Pattern matching primates

Why do we see faces where there are none? Paradolia
Why do we look at random noise and see patterns? Patternicity
Why do we think we have discovered what’s causing filtering if we change one thing and email gets through?
It’s all because we’re pattern matching primates, or as Michael Shermer puts it “people believe weird things because of our evolved need to believe nonweird things.”
Our brains are amazing and complex and filter a lot of information so we don’t have to think of it. Our brains also fill in a lot of holes. We’re primed at seeing patterns, even when there’s no real pattern. Our brains can, and do, lie to us all the time. For me, some of the important part of my Ph.D. work was learning to NOT trust what I thought I saw, and rather to effectively observe and test. Testing means setting up experiments in different ways to make it easier to not draw false conclusions.
Humans are also prone to confirmation bias: where we assign more weight to things that agree with our preconceived notions.
Take the email marketer who makes a number of changes to a campaign. They change some of the recipient targeting, they add in a couple URLs, they restructure the mail to change the text to image ratio and they add the word free to the subject line. The mail gets filtered to the bulk folder and they immediately jump to the word free as the proximate cause of the filtering. They changed a lot of things but they focus on the word free. 
Then they remove the word free from the subject line and all of a sudden the emails are delivering. Clearly the filter in question is blocking mail with free in the subject line.
Well, no. Not really. Filters are bigger and more complex than any of us can really understand. I remember a couple years ago, when a few of my close friends were working at AOL on their filter team. A couple times they related stories where the filters were doing things that not even the developers really understood.
That was a good 5 or 6 years ago, and filters have only gotten more complex and more autonomous. Google uses an artificial neural network as their spam filter.  I don’t really believe that anything this complex just looks at free in the subject line and filters based on that.
It may be that one thing used to be responsible for filtering, but those days are long gone. Modern email filters evaluate dozens or hundreds of factors. There’s rarely one thing that causes mail to go to the bulk folder. So many variables are evaluated by filters that there’s really no way to pinpoint the EXACT thing that caused a filter to trigger. In fact, it’s usually not one thing. It could be any number of things all adding up to mean this may not be mail that should go to the inbox.
There are, of course, some filters that are one factor. Filters that listen to p=reject requests can and do discard mail that fails authentication. Virus filters will often discard mail if they detect a virus in the mail. Filters that use blocklists will discard mail simply due to a listing on the blocklist.
Those filters address the easy mail. They leave the hard decisions to the more complex filters. Most of those filters are a lot more accurate than we are at matching patterns. Us pattern matching primates want to see patterns and so we find them.
 

Read More

Images in the subject line

I’ve seen this trick used by a few senders recently, with varying effectiveness.

Where do they get these pictures?
While you can scatter any images you like across the body of your message, the subject line is limited to just text. But “text” is more than just “a, b, c” – using RFC 2047 encoding you can use any character you like, including many tiny pictures.
⛄ 💰 🐘 ✈ 🎁 ☂
☀|||||||☀
Experian, Vertical Response and Bronto all have some interesting things to say about the effectiveness of using these.
Finding the right glyph can be tricky. Macs have a fairly decent glyph search engine (under Edit > Special Characters… in most applications) while Windows has a fairly mediocre one (Start > All Programs > Accessories > System Tools > Character Map > Advanced View). Both are missing some useful features, though, so I put together something better.
emailstuff.org/glyph lets you search for glyphs by name. It’ll tell you about related glyphs (“helicopter” and “airplane”, or “package” and “wrapped present”) which can help you find the right image when you don’t know it’s name. And, once you’ve chosen a glyph, it shows how to use it in various encodings (if you’re using a GUI tool or a web form to compose your emails you can probably just copy and paste, but it’s handy for manually editing messages when your composition tool isn’t unicode-friendly).
Will all your recipients be able to see these glyphs? All mail clients support utf-8 text and this sort of encoding so the only issue is whether the recipient has a font installed with the glyph in it. That’s operating system specific, rather than depending on the web browser or mail client, so if you want to test – and you probably should – you can get away with just Windows and OS X for desktop, iOS and Android for mobile.
Have fun! But don’t overdo it.

Read More