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CloseReview for Quote Colors by Charles Calvert
Rated 5 out of 5 stars
Very useful extension, though I wish it supported more than five levels (I get some very nested conversations at times). Like jk2jxl, I was able to change the maxVersion value in the install.rdf file and install it in Thunderbird 5. See http://kb.mozillazine.org/Editing_an_add-on_to_change_its_compatibility if you want to do this.
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