Images not loading in Apple Mail...with a twist

Updating this. After a lot of testing, I still haven't figured out the issue. Note that I have 2 domains I use for email content, and 2 unrelated domains hosted at Bluehost.

Things I've done:

Install purchased Cloudflare custom SSL cert (SSL Labs A+ rating) and installed. Not working.

Move domain to Hostgator and use a Cloudflare custom SSL cert. Not working.

Tried different custom certificates from Let's Encrypt, Digikey, and Google and adjusted settings. Not working.

Use an existing subdomain on Bluehost that was never used for anything. Let's Encrypt cert. Not working.

Create a subdomain on Digital Ocean, use a free Let's Encrypt cert. WORKS

Insecure URLs linking images on Digital Ocean also works.

Use random AWS S3 bucket and domain. WORKS

Confirmed this is a macOS Monterey+ and iOS 15+ issue. Last 3 macOS releases load everything just fine.

Through all this, all email privacy controls were turned off. Also tried multiple Macs with random configurations, DNS settings, iCloud settings, and ISPs. I know I can fix this by moving to a working setup but it still leaves 10+ years of archives broken. Next, I am going to wait until the weekend and try moving a domain to Digital Ocean. Perhaps Bluehost and Hostgator are considered a security risk for email content by Apple now. I'm in too deep now, I want to find the answer!

Ahhh okay, thank you. You set me on a different path and I found some previous posts of yours on this issue. I'm using Let's Encrypt on a shared host. The SSLLabs scan gave me an "A" but an alternative domain with my service provider which works has an "A+" with HSTS and stapling both enabled there, along with some older TLS 1.2 cyphers that I don't have with my cert. I'm going to experiment a bit with these settings and see if I can get things to load.

Thank you again for commenting. My cut-rate (terrible) web host wants to upcharge to make any changes to SSL parameters, so rather than give them money I'll just throw my tiny files on an S3 bucket and relink my newsletters. Will be faster, too.

Well, I compared the cert to another that was working and tried to line up the parameters. The only thing I couldn't do was add some of the older TLS 1.2 cyphers or change the issuer (without paying) and it still didn't work. Spun up an S3 bucket and it was working fine in my testing.

The CloudFront idea might be better, though, because then I wouldn't have to change any code on my end and it would reactivate past emails sent for Apple Mail users.

I just modified an email and changed the image links to point to a new (previously configured and propagated) domain. This one has never been used but is on the same IP as the problematic ones previously mentioned. Apple Mail *still* will not load the images which are confirmed working in other email clients. If I click "view in a browser," everything loads as it should in Safari.

The only thing that changed which caused this problem is that the server hosting content went down for an hour, and in that time myself and one other person tried to open an email. All image links from that server have since refused to load.

I just dipped into the Console and saw entries for mail.app as I scrolled through a folder of impacted emails, and there was no obvious error or reference to DNS that made any sense to me. So I don't feel any closer to a solution.

Thanks for the reply, it's a good thought but regular HTTP image links are also not working, and even our newer templates with HTTPS links were working for us previously and are currently working for clients who open in any version of Apple Mail looked into. It's almost like the IP is cached as "bad" somewhere on our computers which are both in different physical locations, too!

Yes, this has no effect.

This is not active or being used. To add clarity, the email accounts being used are hosted at Rackspace and access via POP and IMAP. This issue still exists whether signed in to iCloud or not.