I have been using Mozilla Thunderbird for some time and found it quite sufficient in what it does never needing to or wanting to take it beyond it's construct.

Recently I started to use a calendar application but discovered Lightning, a Thunderbird add-on bringing the features of Mozilla Sunbird calendar application into the same application as your email.

A couple of other add-on discoveries in ThunderBrowse and the Sender Verification Anti-Phishing Extension installed and behold the new found usefulness, well at least all the usefulness I need for now.

And for one last thing I added some aesthetics in the Azerty 'mail 3.0 theme, and I'm now quite a bit more happy with new look Thunderbird application.

Ho hum, carry on. :)