Deliverability & Inboxes: The truth about images in email

As an email marketer and somebody that works closely with customers using open time technology powered by live images, I’m often asked how the inclusion of more images in an email will affect deliverability. Perhaps 5 to 10 years ago, including more images in your email may have been considered ‘spammy’ by mailbox providers but that’s no longer the case. If we go back a few years, the recommended image:text ratio was 50:50, but with an increased focus in design-led email in recent years, email has evolved to be more image friendly. Now, emails that contain nearly all images don’t struggle to be delivered.

Other factors have become far more important to deliverability; the most important factors are reputation, authentication and engagement. Senders that have a good reputation will see their emails being delivered. Those with a poor reputation will be junked. Your reputation isn’t affected by how many images are in the email, or the weight of the images. Reputation is built by sending well coded emails that render well and that people want to receive and engage with - because the content is relevant to them. To keep your reputation, you need to be sending high volume emails consistently, practice good list hygiene and and try to keep complaints as low as possible. In short, including more imagery in email is not going to cause any deliverability issues, it’s a much bigger picture than that.

However, don’t rush out and start sending image only email content. You still need to have html text in there. Generally, we recommend a minimum of 500 characters in the email to negate impact on spam filters. 

Email on Acid did an experiment in 2014 to test the impact of image-to-text ratio on deliverability. Here's what they found:

“By leveraging our SPAM reporting, which tests against 23 of the most popular SPAM filters, we found that if your email has 500 characters or more, content to image ratio does NOT affect deliverability! This finding was contrary to what we'd heard from many marketing resources, so we were surprised to say the least. All of the emails we tested with 500 characters or more got the green light from all the SPAM filters, regardless the number of images added.”

Another image based objection I hear regularly is that some inboxes turn images off by default. It’s true! Some clients do block images by default and some users do change their settings to turn off image;, in these scenarios it is obviously a challenge to relay the message of the email if it's in the images. If you’re using content automation it can mean that you can’t always be very accurate and descriptive in the alt tag, usually because the products are personalised to each individual recipient from 1 html version. In this instance, I recommend using alt tags that are generic enough to get the message across but that are still broad enough to be accurate for all recipients. For example, in a product based recommendations email, for the product alt tag you could use ‘Products picked specifically for you Jordan’.

However, I do believe that since Gmail made the move to default images to ‘on’ in 2013, that this has become much less of an issue. With the majority of inboxes now defaulting to images being displayed as standard, and the huge volume of users using native iPhone/Android apps with images on as default, emails containing multiple products will still perform very well. Personally, I don’t see image blocking as a big deal – after all any recipients that are engaged should download your images – and there are ways to overcome this challenge with alt tags. You can also ask recipients to ‘whitelist’ your emails by adding you to their safe senders list (it's a good idea to include this in your welcome email BTW).

So to wrap up, images are really important to deliver a good email experience and long as you’ve got at least 500 characters of text in the email and good, descriptive alt tags, there’s no reason why moving towards an image-heavier approach should have any negative implications.


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