Batch Add Email Addresses with AddressContext

All platforms running Thunderbird: The addressContext Thunderbird extension batch processes to and from email addresses for a set of messages from the context menu. Quickly create a new mailing list, or simply add new cards to your address book by selecting a set of messages, right-clicking and choosing “Add Senders/Recipients as Cards” or “Add Senders/Recipients as List.” The addressContext extension is a free download, and works with and wherever Thunderbird does.

addressContext [Thunderbird Add-ons]

I should really create a list of these addons and make them public!! I might do that later!!