This is a problem that appears randomly and often the same newsletter opened with different clients (Gmail, Outlook, Apple Mail, Yahoo, Thunderbird, Office 365, …) shows different behaviors. Special case is when the images are not shown on iPhone.
Short answer: it’s not a problem with your newsletter or the Newsletter plugin. But let’s see in detail what can be the reason.
What's inside
- Case 1: the email reader is blocking the image loading (most common)
- Case 2: your site is blocking the image download (rare)
- Case 2b: your site is blocking Apple Mail and iPhone
- Case 3: your site is blocking Google, Apple or Microsoft (hard to spot)
- Case 4: the picture has been deleted
The first thing to know is that Newsletter just inserts in your emails a link to the picture. For example, if we send a newsletter from our site, www.thenewsletterplugin.com, containing images, they’re just referenced in the content as https://www.thenewsletterplugin.com/wp-content/upload/…
Images are not embedded in the email and when reading the message the receiver needs to be connected to the internet to see the images.
Case 1: the email reader is blocking the image loading (most common)
This behavior is especially shown by Microsoft Office/Outlook which blocks the image loading and shows a little label in the image space saying to click to load the image. Sometimes, it depends on the Outlook version, even one notice on top of the email is displayed asking if you want to load the images.
Outlook is not alone: Gmail has this feature and even Thunderbird. In every case, a notice, sometimes not so noticeable, is shown.
Case 2: your site is blocking the image download (rare)
It was a configuration widely used some time ago, the so-called “image hotlinking block”. In practice, the site (actually the server) is configured to not respond to image requests if not coming from a browser visiting the site.
An email client which needs to get the image is not a browser surfing the site and so… it won’t be served at all.
The solution is to remove to hotlink block usually available on your provider management console.
Case 2b: your site is blocking Apple Mail and iPhone
Apple Mail since OS X 15 and Apple Mail with Mail Privacy Protection (MPP) activated use the User-Agent “Mozilla/5.0” when requesting the email images to show them.
That User-Agent is sometimes blocked by providers because it is missing common parts, like the OS and other information. Apple uses that kind of User-Agent to send as little information as possible to get the images.
So, if your Apple Mail is not showing the images in your newsletter (but they’re shown on other clients), try to report this case to your provider.
The problem can be tested using Firefox and a User-Agent switcher add-on. When the User-Agent is forced to the value “Mozilla/5.0”, if you try to open an image of your site it will be blocked (many kinds of answers are possible, the most common are “403 not allowed” and “406 not acceptable”).
How to test this problem
- Get the URL of an image from your blog, let’s say it is
https://www.yoursite.com/wp-content/uploads/image.jpg - Go to reqbin.com/curl: that service lets you make a “call” to the server to get the image like browsers or email clients do
- Use the command:
curl https://www.yoursite.com/wp-content/uploads/image.jpg -A "Mozilla/5.0"
If the result is an error (code 4xx), your provider is blocking all requests with User Agent set to Mozilla/5.0 which is the one used by Apple.
Case 3: your site is blocking Google, Apple or Microsoft (hard to spot)
Google, now even Apple and maybe Microsoft, to protect your privacy, don’t let their email readers download the images from your PC directly. They download them for you on their servers so you get them from their servers and not directly from the email sender.
That denies the sender the possibility to track the image download and get, for example, information about your IP address (which in turn can be converted into an approximative location).
If your provider has rules to limit the number of connections from an IP address or has a filter set manually or automatically against those email providers, they won’t be able to get the images and your recipients won’t see them.
This issue is very hard to debug and we see it very few times: for sure it is not the first thing to indagate on.
Case 4: the picture has been deleted
It sounds like a joke, but it happened. Of course, if you delete a picture referenced by a newsletter (remember: emails do not contain the pictures!) it won’t be shown.