Best version?

ESR is an annual version that gets regular security updates, but not new features. Release is the bleeding edge where you get all the new features fortnightly, along with their inherent bugs that come with all new software features. Especially with a product like Thunderbird with over a million lines of code and more than 20 years of code history and interdependencies. Originally ESR was intended for mostly corporate use where frequent update cycles can be counter productive, but those of us that rely on functional add-ons tend to like it because developers have a year to get a new release of their add-on ready as opposed to a two weekly release schedule and we get the security patches.

Thank you gentlemen. I'm still a bit unclear how to do this via Debian. Do I uninstall and reinstall or would upgrade do it? I understand about altering sources.list tho.

I'm still a bit unclear how to do this via Debian.

To do what exactly?

I understand about altering sources.list tho.

Not running Debian here, so I don't know what you're up to.

No problem, I'll figure it out. The doc isn't quite clear as to what to do with the installed version, whether it will be automatically replaced or has to be uninstalled first. Some Debian user might read this thread and know exactly what to do. No rush either, I'm happy with the esr version anyway. Only complaint is that I find the search feature to be very unintuitive but since developers always like 'features', things always get more complicated whereas I have a strong bias towards simplicity.