You can bump up the maxversion in the install.rdf of your xpi file. I've tested it on Shredder/3.0b3pre (the development branch of Thunderbird) and it works fine.
You can bump up the maxversion in the install.rdf of your xpi file. I've tested it on Shredder/3.0b3pre (the development branch of Thunderbird) and it works fine.