Avaliado com 4 de 5 estrelas

This is a time saver, and actually works with later versions of thunderbird via the checkCompatibility add on which disables the compatibility checks.
The one issue I noticed as more move to gmail is it does not identify correctly the quoting gmail uses in html emails.

Esta análise é para uma versão anterior do extra (0.9). 

Thanks for the nice review.

As for HTML quotations: Thunderbird does not recognize them as such, therefore QuoteCollapse cannot act on them, unfortunately - that is, I have found no way around so far.