Apple Mail Blue Question Marks Instead of Images?

System Preferences>Network, unlock the lock if need be, highlight the Interface you use to connect to Internet, click on the advanced button, click on the DNS tab, click on the little plus icon, then add these numbers...

8.8.8.8

8.8.4.4

Apply.

A “nanny filter” is a slang term for a content filter. Filters can be installed and running on the Mac, or on an intermediate device such as a firewall/router box, or at a DNS provider (which is what BDAqua was aiming at) or at an ISP.

This filter blocks access to certain web sites and/or certain materials.

The Apple Parental Controls are one example, and there are many other (and inevitably failing) implementations.

ISPs can routinely block large attachments.

Check your firewall. Those can sometimes incorporate filtering and anti-malware features. There’s often a web login to check the firewall settings.

Check your Comcast ISP mail settings, using the Comcast ISP mail web interface. Look for filtering there.

Check with smaller attachments on your mail messages. Again, ISPs can block larger attachments.

Make sure your ISP mail connection uses SSL, as that can prevent intermediate devices from monitoring and modifying the data.

As this is happening only with Comcast, this really seems something specific to that path, and to the Comcast servers.

Please download EtreCheck and run that, and then post the hardware and software configuration report here.

Open a new reply here, and then press the button that looks like a printed page to get a text input box big enough to paste the report here.

From that report, we might be able to spot something here that’s blocking access. Maybe some add-on security tools, for instance.

It’s also possible to block remote image loads. The setting for that is in Safari.

BDAqua wrote:

Well, something is failing, could be HW.

Given this is reportedly isolated to embedded images within mail messages, hardware errors are unlikely; that’s a pretty specific error. This reeks of a network nanny filter, malfunctioning add-on security tools, or a mail server that’s stripping off attachments.

Oh, if you click or right click on the blue question mark... any options?

Such as a download or a view image item, for instance.

Bruce Kieffer wrote:

Fingers crossed. I think you found the answer Mr.Hoffman. You said "I’d expect the domain name field to be a domain name and not an HTTP URL, but that won’t effect this." I removed the http://www. on both routers, and now I see the images in my emails. I will test for a few days to be sure this is a solid fix. Thanks.

I would absolutely log some Apple feedback on this, as this sure looks like a bug. AirPort and all are deprecated products of course, so the feedback might go nowhere, but a bogus domain specification should not cause what’s being seen here. Point to this thread in the feedback, too.

Okay, so a macOS-only install with no add-ons shows this?

That’s either a macOS bug, or it’s a nanny filter or firewall filter or otherwise involved, or the ISP, then.

If not, and if the test install had the same or similar apps installed...

I see an app cleaner helper, and the Cocktail (among other uses) app cleaner, and some mail-related add-ons.

I’d start by removing the app cleaners and the mail add-ons per the vendors’ instructions, rebooting, and trying again.

App cleaners can sometimes cause corruptions that can require a re-installation, unfortunately. Not a class of app I generally recommend.

As a side note on potential corruptions, and given these are present here: Using third-party apps to remove duplicate photos might damage your Photos for macOS library - Apple Support — and there are related crashes. There’s not much I’m aware of to fix those, short of exporting and re-loading photos.

Given Mail is centrally involved, I’d test without Deliveries and Unibox, too.

If the above does not work.... I’d suspect this might then be headed to a backup, another backup, a wipe, and a re-install, migrating in documents and files only, and without migrating over add-on apps. To starting over, and seeing if the issue persists in a newly installed environment.

That Comcast box connecting your network wiring to Comcast wiring? More often than not, that is a firewall.

The SSL settings are in the mail account settings.

Ring up Apple Support. Somebody is probably going to need to poke more directly at this Mac.

I too suspect it’s a Comcast setting.

Have you logged into the Comcast web mail portal and looked around?

What box is providing your firewall and NAT services here? That modem looks like it might actually be a “just” modem, which means there’s usually some other device or box connected to that to provide firewall and NAT and DHCP services.

Can you try this Mac elsewhere, off the Comcast network?

Chatted with Comcast support?

Checked the Comcast router settings?

Checked the Comcast web mail portal for any no-remote-image-load relevant settings?

Okay, from your previous replies, other devices here are working on this network, with the same email account?

And these same messages are working correctly on other clients, attachments and all?

And these are attachments, and not remote images?

I’d expect the domain name field to be a domain name and not an HTTP URL, but that won’t effect this.

75.75.75.75 and .76 are the Comcast DNS servers. Those aren’t involved. Switching those to 8.8.8.8 and 8.8.4.4 would prove that.

If other devices are working on this same Wi-Fi and with this same email account, and if your tests with a scratch macOS install had absolutely NO add-ons and NO add-on security and NO add-on cleaners and NO add-on content filters and NO add-on ad blockers and NO add-on VPN clients and NO VPN connections—that is, just a new install of macOS High Sierra, Mojave, or Catalina, and with a manually configured and not-restored-from-backup and not-migrated email account set-up for this Comcast account—then we’re left with... well... nothing.