Thunderbird is great. Just a suggestion: when you have open a loto of tabs (usually single emails open in new tabs or reaserches or attachements) and you want to close many or all of them is annoying that you start clicking on the "x" to close the first and than move a little to close the other one, and than move again a little to cloes the next one and so on. It would be easier and quicker to let the tabs' top be all the same lenght when you are closing them so you can do it quickly without moving the mouse and after a few seconds the remains tabs' top could take the original lenght. Pratically the same as happen with Chrome tabs.
Thank you