Easy-Email

When you use Thunderbird 2 with the Easy-Email solution it works as you are used to, however it will synchronize with Gmail instead of downloading emails.

You can choose to download a copy of your emails so you can work offline as well. This means you will be able to read and respond to emails when you are on a plane or a train for instance. Once you get an internet connection again your emails will be sent.

You can choose which emails to have a local copy of on your computer by adjusting the Synchronization Settings.

If you have your old emails stored in Thunderbird 2.0 you will probably want to copy them to Gmail. This will make the emails available to any client you synchronize with Gmail.

Initially you setup email synchronization without making changes to your old email setup. This allows you to try out Easy-Email without affecting the way you used to do email.
When you have decided which solution is right for you, you need to turn off either your old email setup or the Easy-Email setup. This section explains how to turn off an email account.

Gmail organizes emails in threads. Responses to an email are grouped with the original email making it easy to follow an entire conversation.

This How To guide explains how you can create a signature in Thunderbird 2.0. 

Thunderbird 2.0 has an add on, which automatically synchronizes its address book with Gmail.