JR2
Do hi-res images in a campaign affect spam scores?
With retina screens becoming more popular, many email designers are using hi-res images to keep their designs nice and crisp. This begs the question: Do hi-res images affect spam scores and deliverability?
My intuition tells me that the potentially larger image file sizes could hurt your spam score and deliverability for some clients, but I don't have hard data to back that up.
Any deliverability experts have insight into this?
Fantastic question. I'm not aware of inbound spam filters that perform GET (or HEAD) requests on images within the HTML part when scoring a message. We can tell if they are doing this by requests made to tracking bugs, such as Email Analytics', but we don't ever see these requests. Without performing a GET or HEAD request for an image, there's no way to determine its size.
After examining SpamAssassin's rules database, they do use two variables within their rules:
Actually fetching the image to determine its size isn't something they do.
That said, some ESPs perform pre-flight, outbound spam checks. These can be more sophisticated because they have more information to hand (such as file size of images, sending volume in advance etc). It wouldn't surprise me if some ESPs perform checks on image sizes and score lower as a result, but I don't think this is anything to worry about.
This is great to know Matt, thanks very much. I can confirm that our email client, Epsilon, scores you against using large images but its not clear if it looks at the file size or the pixel dimensions.
@Jason, perhaps this is a wrong place to ask (didn't find anything anywhere else). Has there been any exploration on using hi-res images as background images? Typically you put an image double the size in a half the since max-width; Table = 700px while the image is 1400px. Looks like background-size: cover fixes the issue but its stripped out in Gmail.