Do you have View/Message Body as set to Original HTML? Does it look the same in safe mode (hold Shift when you launch TB)?

sfhowes said

Do you have View/Message Body as set to Original HTML? Does it look the same in safe mode (hold Shift when you launch TB)?

Yes, I have Original HTML set for Message Body. I tried setting Simple HTML as well as Plain Text, but got same result.

Safe mode also didn't help.

Regards.

The other odd thing about your picture is the Header Pane (top of the Message Pane) has the usual buttons, but not the From, Subject and To headers. I don't have a solution yet, but maybe by resetting the resetting the Header Pane (right-click, Customize, Restore Default Set), it will change.

http://kb.mozillazine.org/Toolbar_or_windows_layout_not_working

Do you have any kind of antispam/antivirus program scanning mail?

Though I'm using AVG Antivirus for scanning mail, the Header Format mention gave me the clue.

I was using an extension "Thunderbird Conversations". Looks like it requires an update for being compatible with Thunderbird 52.*, as it works nicely with previous version 45.8.0.

After disabling it, now the Message Pane is back to normal.

(Snapshots attached.)

Thanks a lot for the help, I really appreciate it !

Regards, Rajesh.

Thanks for reporting your findings. I could see in your first picture that the Conversations add-on was in use, but concluded that add-ons weren't the source of the problem since safe mode had no effect.

I think Thunderbird doesn't launch in safe mode on my laptop when I hold shift key while launching it. That's why I said it had no effect. My mistake.

When I use "Restart with Add-ons Disabled..." option from Help menu, Add-ons get disabled. I should have tried it earlier.

Anybody else using "Thunderbird Conversations" extension ?

Regards, Rajesh.