I have this issue as well, but slightly different. I can still right click any recent message and 'open message in conversation'. I have two issues, but they are slightly different but fundamentally the same. Note: I can understand an email that I have received and not replied to having no 'conversation'. Issue 1) If I reply to an email, I cannot 'open in conversation' on the email I received to view my reply email. Issue 2) If I select an email that I know has a long conversation (3+ emails each from myself and the other person) then it will try to 'open in conversation' but it may or may not work. Sometimes it does work, sometimes it seems to look for a conversation connected to another email. Based on the subject line, I may have deleted the emails that it is trying to use in place of the one I selected. --- Trying from the 'Sent' box, it seems to work better... with one exception. It seems that if I reply to an email and don't receive a reply to my email then the 'open in conversation' only displays my sent email and not the original that I replied to.

The 'Open Message in Conversation' command works here even if there is only one message in the thread. The first thing I'd try if it's not working is start in safe mode (hold Shift when TB is launched), in case there's an add-on, among other possibilities, that is incompatible.

Thank You sfhowes for the suggestion to start Thunderbird in "safe mode". I did and when I launch Thunderbird in "Safe Mode" (by holding Shift when starting TB), I am able to see the "Open in Conversion" option when I right-click any message. So now, I'm not sure how to proceed. Should I simply use Thunderbird in "Safe Mode" all the time? As far as I know I am using Thunderbird as provided. I have not consciously installed any "add-ons". I have installed add-ons on Mozilla Firebird, could this result in add-ons also getting installed on Thunderbird?

As long as you're not using any extensions or non-default themes (see Tools/Add-ons), the next thing I'd try is launch in safe mode, check the box 'Reset toolbars and controls' and click 'Make changes and restart' (see the safe mode kb article). This will repair a broken layout, if in fact that is the source of the problem.

Thanks Again sfhowes ! I followed your instructions and now I see the "Open in Conversation" choice when I right-click a message which has at least one response. Problem Resolved.

Help ! This time, even when the option to "Open in Conversation" does appear, when I click on it, nothing happens ?!? I believe there has been a Thunderbird update since I last tried to use this feature. I tried starting the program in "safe" mode, but no help. I'm using Thunderbird 52.4.0 (32-bit) the current version.

If you right-click a message and select another command, such as Forward or Save As..., does TB respond, or does nothing happen?

Yes, all other commands (reply to, forward, open in new tab, etc...) all work fine. It is just "Open in Conversation" that does nothing.

Is the result any different if you select a message and then Message/Open in Conversation, or Ctrl+Shift+O? Press Alt to show the Menu Bar if it's hidden.

The right-click method works here in TB 52.4.

No, selecting the message and the "Message" drop down and "Open in Conversation" does not work, and neither does selecting it and CNTL-SHIFT-O.

Here's some more strangeness: This e-mail exchange has 4 threads. Right-clicking each shows the option "Open in Conversation" on 3 of the 4 messages. On 2 of these messages clicking on "Open in Conversation" does nothing. But it works on one message. The only thing that is different about this message is that it does not have the flag showing the message has been replied to. So, it appears that once a message is replied to, it won't let me "Open in Conversation"? Weird.

Update: I looked for another "conversation" and I am noticing a similar problem, but this time, most "unanswered" message open in Conversation, but I found at least one response that sucessfully opened in conversation, but about half or more threads of this e-mail exchange do not respond to clicking "Open in Conversation". I don't know why.

If it works for some messages but not others, I'm guessing that there is something malformed in the headers of the non-working ones that produces the non-result, e.g. the threading has been broken either by the mail server or the email program of the sender.

Thanks. If I find the difference, I will post it here.