Let's hop into the #Thunderbird Time Machine for a look back at Thunderbird 3.0!
Released on December 8, 2009, v3.0 introduced a Migration Assistant to let you easily activate new features (like Smart Folders and a redesigned Toolbar) or stick with the old ones.
#Thunderbird 3.0 also saw the debut of the Add-ons Manager (but in very, very beta form), letting you extend the functionality and visual look of Thunderbird with themes and new features.
Plus, it introduced tabbed email view, new account setup wizard, and... wait for it... auto-downloading of IMAP folders! 
Version 3.0 of #Thunderbird also ditched compatibility for Windows 95, 98, and (
)ME.
The organization that developed and produced #Thunderbird 3.0? Mozilla Messaging.
Hope you enjoyed this blast from our past. Let us know if you personally used Thunderbird 3.0 back in the day. #tbt #ThrowbackThursday
(Here are the archived release notes: https://website-archive.mozilla.org/www.mozilla.org/thunderbird_releasenotes/en-us/thunderbird/3.0/releasenotes/)
@thunderbird oh yeah it was key in the office. We went from the suite to Firefox and Thunderbird.
@thunderbird Windows Me? Blah. Give me Windows 2000.
@thunderbird Back in the day? I use Thunderbird now. It works! :--)