Interested to know before hand how the next version of Thunderbird (be that a beta release, a full release ) is going to look like ?
Interested in experimenting with new features before they are made available to a wider audience ?
Well it's possible and kind of easy, the QA team of Thunderbird as setup a low traffic [1] mailing list where we announce Test days (which are
when new features get tested by a wider audience). Those announces are made when the feature is ready, and unlike on nightly builds it should be fairly stable when the announce is made.
So how can you join this mailing list ?
[1] can be verified here : https://mail.mozilla.org/pipermail/thunderbird-testers/
Sure, a dummy account helps. But it's not the same as doing real work with it. With Firefox/Minefield I do really use the product. With a dummy account I'd just try a few random things without much relevance to my real world usage (like e.g. my multi-gigabyte profiles). In a few months I'll probably find time to setup something which I can use in real live and still don't have to fear any bad consequences.
I understand your concerns about your email. You still can setup a dumy account - that would help.
I test Firefox/Minefield builds almost daily (using it as the somewhat default browser on one of my computers), but I never test Thunderbird builds. I certainly could, but I don't dare to use my "real" mail accounts for testing. Somehow my mail seems to be to important to risk anything with it. I probably could set up a dummy account and copy-forward mail from one of the real accounts to make sure nothing gets lost...
P.S: Without JavaScript posting comments fails.