According to http://kb.mozillazine.org/Files_and_folders_in_the_profile_-_Thunderbird

"The permissions.sqlite and content-prefs.sqlite files store the permissions for what remote content can be displayed. Lightning also uses that file."

Try renaming the two files with .bak extensions, with TB closed, then restart TB and see if it resets the remote content options. You might have to do the same with blist.sqlite.

Thanks. Renaming those files allowed the yellow bar to return and for me to tell TB to show all remote content in the emails. But the embedded images still didn't show up. The mystery continues.

Are the images visible when the account is viewed in webmail, i.e. are they blocked by the mail provider before they're downloaded to TB?

Are the images visible when the account is viewed in webmail, i.e. are they blocked by the mail provider before they're downloaded to TB?

Works in webmail, works on my phone where I use K9. I run my own mail server and I host a few websites for local small business. Thanks for asking. Works on my laptop where I also use Thunderbird. Both desktop and laptop run Linux Mint 20.3.

It is definitely something with my desktop Thunderbird profile/install.

I don't know why the images would appear on the laptop but not the desktop, all things being apparently equal.

Is there any external security/antispam/AV app on the desktop that could be blocking remote content? If there is some non-obvious setting in the current profile causing the issue, you could try adding an account to a new profile and seeing if there's a difference. Help/More Troubleshooting, about:profiles, to create and manage profiles.

I don't know why the images would appear on the laptop but not the desktop, all things being apparently equal. Is there any external security/antispam/AV app on the desktop that could be blocking remote content? If there is some non-obvious setting in the current profile causing the issue, you could try adding an account to a new profile and seeing if there's a difference. Help/More Troubleshooting, about:profiles, to create and manage profiles.

I received your reply in my email, and the yellow bar is there allowing me to show remote content, and everything shows up properly. At some point I have either blocked remote content in these Substack emails or from these recipients. A long time in the past I had an AdBlocker add-on in this TB profile but it has since been removed.

There is no active antispam extra running. Since I'm on Linux I don't really use AV software, - ClamTK is installed but not in a way as to interfere with email. My laptop has the exact same setup.

If it isn't those first three files mentioned in the original reply, there must be some other file with blocking rules which is nuking the content. The weird thing to me is that the Remote Content Exceptions list has only Allow rules and no Block rules but that may be neither here nor there.

If there is some leftover setting in the current profile blocking the substack images, it will probably not be present in a new profile, so that is why I suggest it as a test.