Quick Look not displaying content of .eml files

My testing shows, at least on my M1 OS X 11.2.3, that it isn't .eml files that are the problem, it's specifically .eml files generated by Microsoft Outlook which do not appear properly in Quick Look. The same emails saved by Apple Mail do show up properly in Quick Look, as do .eml files I generate using Emailchemy to convert from .msg files.

As best I can tell from discussions about this, the problem is that Outlook does not use unix linefeeds.

And an Automator folder action that removes the CR line-endings from the Raw Message Source (.eml) files when they are saved to that assigned folder, in this case, the Metadata folder on my Desktop because it was handy:

One can view these entire .eml files in Quick Look after the folder action has triggered by the save operation. Tested on macOS 11.1, but should also provide a solution on Catalina too.

I've got Big Sur 11.1 and am able to use Quicklook on .eml files and see the contents:

Boot into Safe Mode by booting with the Shift key held down and check there to see if the problem persists.  Reboot normally and test again.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

I also could not display .eml files in quicklook for some files but not all. I was able to recreate the error but I'm still not sure why that is. If I save the email from Mac mail as a "Raw message source" it does not work in Quicklook. However, if I just drag the email to the desktop, that new file is now viewable in quicklook. Does this work for anyone else? Drag and drop seems to work for me.

In Big Sur 11.1, when one saves an email from Apple Mail as a raw message source, it writes a *.eml file, whose content has carriage return endings on every line. When one drags and drops an email onto the Desktop, it has no carriage return endings.

When one strips the CR line endings from the *.eml file, Quick Look will display its entire content.

I have submitted a bug report to the Apple Mail team to fix the saved Raw Message Source from the evil of carriage returns.

In the Terminal, one can remove those CR line endings from a *.eml file by following the procedures here (and on macOS, using the control-V/control-M approach in sed).

Big Sur 11.1 permits viewing of the .eml mail header, but the content is absent. This worked in Mojave 10.14.6. I suspect that in Catalina or Big Sur, one must save to Rich Text format, text, or PDF to benefit from Quick Look.

You can send feedback to the Mail product team about this issue, though no fixes will be forthcoming for Catalina now.

Well, Big Sur 11.2 will eventually get released, and I will test this again with it.

Could not see the content of any saved .eml here on my M1 mini with 11.1. Interesting.

I only use Apple Mail. No assurance that Thunderbird is writing the same .eml content as Apple Mail though.