Thunderbird Conversations is a Thunderbird extension which, as the name implies, enables a conversation view in your Thunderbird. Notable features include:

- a regular conversation view that fetches messages from all folders, and behaves just like Gmail’s

 - integration with Thunderbird Contacts: participants have tooltips in the conversation, and you can view their avatars and profiles from Facebook, Twitter…

- a quick reply feature, with autocomplete, that allows you to reply to a thread in a snap.

In addition to threading enhancements, Thunderbird Conversations adds many features to Thunderbird, obsoleting several other addons.

CompactHeader
Add symbol in header plane to switch between compact and expanded view. Options to switch between one or two lines compact view, which buttons should be displayed in header pane.

RSS Linkify Subject
Linkify Subject header with Content-Base URL when viewing RSS item to easily open it.

Slideshow
Displays a slideshow of picture attachments. When email has attached pictures, it displays "View as Slideshow" button next to the attachment. Button click pops a slideshow window with all the images, allowing you to zoom in/out, save.