Rated 5 out of 5 stars
ExQuilla is great addon and actually IS worth spending 10$ a year.
I'm also a company worker and of course I can use MS Outlook or web access for free. But because I prefere Thunderbird I found ExQuilla just the solution I need. It's fast, works fine and Kent James is doing great job to make it better. Why so many people think it should be for free? OWA is free - you can use it if that's your choice. Or you can write your own Mozilla Addon.
I have just purchased my license.