We, at Pure360 had a interesting twitter exchange recently about why image only emails get through even though spam checkers given them a high score. To avoid further 140 character chats on the subject I wrote this:
Savvy email marketers will know that it is not recommended to send big image emails as they are far more likely to be junked, so why is that sometimes they managed to get through?
Many people who use an ESP will have a spam checker built in. The most commonly used one (of many) is Spam Assassin. On more than one occasion we have blogged that text to image ratio should be 60:40, in favour of text. The main reason behind this is because of the spam assassin warning.
This was not a decision that was just made up by the guys at Spam Assassin, it was a rule that evolved from the fight against spam and filters’ ever changing rules to adapt to spammers’ techniques, who in turn adapt to beat them…check out Spammers vs The spam filter for more details.
Additionally, the big ISPs don’t rely on Spam Assassin. While they may well share many of the same decision making and may even refer to it they each tend to have their own rules and algorithms that have evolved over time and competition with each other to have the better junk filter.
This does not mean that all heavy image emails will go to junk or be junked by recipients or that the big ISPs will let them all through. However they will have a harder time getting delivered than emails with a good ratio, but it is also about rapport. If someone who does not have a good ‘digital rapport’ with your brand cannot see what the email is about with the images off, they are less likely to prioritise it and more likely to hit the spam button.