Not all images are displayed
The last few versions of Thunderbird appear to be broken, or so I see it. I'm currently on version 60 on Windows 10. Images in mails either do not show or only some images from the mails show. The exact same mail on print preview almost always shows the images. I say almost always, not always.
When was this last working: I'm not exactly sure but I have noticed that each time Thunderbird updates it gets worse. Almost like some image blocker is active. It all started about the time Thunderbird changed the display rendering engine. It was subtle at fist but now I'm to the point that less then half the email images are showing.
What have I done: Better question is what haven't I done.... i have changed the different setting from Original HTML to Simple HTML and the missing images are also not shown but placeholders are, but the placeholders are then for all images and not just the missing ones. I have disabled all add-ons. No change. I have completely removed Thunderbird and installed it new. but kept the mail data. No change. I have removed the mail data and re-entered all the account information new. No changed. I have forwarded the email to a different email address (gmail). The entire content is visible in that application, however triggers the SPAM filtering on the mail. I installed Thunderbird on a different computer and entered the account information. Same missing display.
Mails missing images are generally newsletters, if I email myself several images these all show. This appears to be, currently, newsletter mails only. And if someone forwards a newsletter mail their images are shown but the newsletter is not. i.e. the remote content is often not displayed.
Summary: Since version 50 something, Thunderbird displays fewer images with each update. Same mail on a different client is shown. There are no add-ons causing it. My Email host is not filtering the images out (it is a paid domain and I have confirmed it with them). Thunderbird Email content display appears to no be able to handle the images like previous versions did. Happens so far with newsletter mails, specifically with remote content images.
I most likely missed something in my tests, and welcome anything that will resolve this.
I'm positive someone will say I need to enable the images (yellow security bar) - in settings I have the 'allow remote content in messages' on thus I do not get that bar as the images are always downloaded. Someone will also say that is working just fine for them, and it is possible, but this is my mail and w are most likely not getting the same emails, so that isn't a solid method since we need the exact same mail as a reference.
Wšě wotmołwy (1)
Thunderbird 60 is no longer supported, so even if someone finds a bug, it will not be fixed. Thunderbird 68 also is approaching end of life and will the replaced with 78 in the coming weeks. I will not spend time troubleshooting the old version sorry.
You have made no mention of your anti virus solution, yet between that and bad email structures the vast majority of image display issues are covered.
Thunderbird does have issues displaying inline attachments that are displayed using CID, See https://bugzilla.mozilla.org/show_bug.cgi?id=61815
Other know issue are show in the depends list on this bug https://bugzilla.mozilla.org/show_bug.cgi?id=1405234