I will make the same comment I made on another post regarding Firefox and Mozilla: a few tips from from no one: 1. Rewrite the Mozilla mission statement. I read that and have no idea what your organization does. Mission statements seem like corporate naval gazing, but if it is honest and well written it keeps everyone focused on what you are working towards. 2. Refocus on Firefox R&D and core technologies - Firefox n…
But I couldn't disagree more with number 3. Thunderbird is always going to be a niche product with a much smaller potential user base than Firefox.
More or less every corporation and every individual user out there is a potential consumer of Firefox--every single one who uses the web.
Thunderbird? Not so much. Many consumers prefer web-based e-mail clients or e-mail clients tied directly to the e-mail platform they are using (Gmail, Outlook.com, etc.). And Thunderbird is never going to replace Outlook for corporate mail. Thunderbird is only useful when you want a generic feature set, and it mostly competes with other niche mail clients.
Basically, every dollar invested in Thunderbird is a dollar that could be better spent on Firefox (or MDN). If anything, they should spin off development of Thunderbird into a separate company with its own independent funding structure.