A few useful Thunderbird extensions:
- Display Mail User Agent - adds an icon showing the mail client used by the sender; it could add other icons for operating system and mailing list manager for example.
- Contacts Sidebar - adds a sidebar, below the accounts, with all your contacts; use F4 to toggle.
- Display Mailing List Header - a bit tricky to use a this point (it is at version 0.1), you have to show all headers (View / Headers / All) in order to see it; a menu entry specific for mailing list messages would be nice, it could also add actions like Reply to List and Reply to Sender Only.
- Mail Redirect - adds a bounce action (Message / Redirect - Ctrl+B).
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