Mail not loading images from specific server in iOS15

I’d look for an incomplete certificate chain being offered by the webserver; everything from leaf back to but excluding the trusted root.

Also for any blocks that might prevent images from being cached by intermediate servers, with Private Relay enabled on the client.

Post some testing URLs, and maybe somebody will check the webserver certificates for you.

Or embed the images into the mail messages, and the broken-image issue goes away. (Yes, I know the central purpose here is tracking advertising recipient attention—private relay makes remote image load tracking rather less effective, and which means tracking involving Apple gear is already getting more difficult. Once the recipient clicks on the image, sure, your tracking is available.)

Jason1242 wrote:

Is there a particular SSL cert you'd recommend? I'm planning to try a cert from Let's Encrypt to start.

What I recommend is not using his whole approach; of embedding the images into the message.

LetsEncrypt certificates are free, and should work on any recent Apple products. This so long as the certificate chain from leaf up to and excluding the root is served from the web server.

LE certs will only work with macOS 10.12.6 (2017) and later, and from contemporaneous and newer iOS versions, or when the user has loaded and trusted the updated LE root certificate on an older version. As LE certs are widely used and common, uses on older versions are already aware of this.

Jason1242 wrote:

Is there a particular SSL cert you'd recommend? I'm planning to try a cert from Let's Encrypt to start.

No, sorry. SSL certs are crazy complicated. When people have posted these questions before, they always had some custom SSL cert. I would debug it using my ssl.com or Let's Encrypt certificate and those would work fine. But even with ssl.com, the choices are mind-boggling. I usually pick the cheapest one that has organizational validation. The domain validation ones don't work with older operating system versions.

My current project involves moving all of my websites to AWS Cloudfront for no other reason than being able to use AWS's super-easy certificate features. I haven't tried an AWS certificate with this particular Mail issue, but I would be very surprised if it didn't work.

Apple is very picky about the SSL certificate and doesn’t document exactly what certificate features are required. The only fix is to get a different certificate.