I would like for Thunderbird to show replies to threaded messages in with the received messages. Is this possible, even with an extension?
The desired behavior would be something like how Zimbra's threaded email view works.
GMail Conversation View does what you want without having to copy replies into your folders. Sometimes it doesn't properly pull in your replies, and it doesn't start conversations if you initiated them, but it is the most similar to gmail I have found.
It "is" built-in on thunderbird now, if you do the right steps:
Go on its properties at "Select the folders to search:"
and click on "Choose...", you will see that your top inbox is checked;
just check the "sent" one, click "ok", and "Update".
Now, go to your top "inbox" that is the global one, activate the threaded column and you have a three with all incoming and outgoing messages!
Obs.: thunderbird version 31.4.0 here.
PS.: follow @hvd comment below to restrict the messages shown to a single account (in case of multiple email accounts)!
If you use Gmail. Your thunderbird will sync the folder structure which includes an "All Mail". Use this folder instead of "Inbox" and use the threaded view will make the threads include sent replies.
I prefer this way to the plugin "Thunderird Conversations" because the plugin is very slow to load when the thread is very long. And sometimes the plugin doesn' t display attachments properly. And this way avoids the extra costs of the option "Place replies in the folder of the message being replied to" will incur.
For other mail users, adding a new virtual folder might also do, see: Combine in- and outgoing mail in Thunderbird in one folder . This inspired me that Gmail includes such a folder already.
Yes, Thunderbird can show sent replies in a threaded view.
Open Message in Conversation.
A new tab will open showing the messages in a thread pulled from both 'Inbox' and 'Sent Mail'.
I wish this was available directly in the Inbox but it's better than nothing.
I use the Copy Sent to Current extension to do what it says.... that way I have my sent emails in the sent folder for archival purposes as well as in the folder I was in when I composed the email. That combined with the threaded view gets me the perfect conversation.
Edit: the only problem is that when you search for a conversation, it displays the replies both from your inbox/archives folder AND the sent folder, so perhaps you don't want to use this. But I thought I'd put the option out there.