Almost a year ago Ubuntu uploaded thunderbird-locales for Thunderbird 220.127.116.11. As the Hebrew localization wasn’t ready then, they dropped the hebrew l10n package & files.
During the last year Mozilla released more localizations for Thunderbird, but it doesn’t seem Ubuntu updated their package since the initial upload. In the same period Debian (thanks to Daniel Baumann) has added 5 more languages (some are unofficial localizations), including Hebrew.
The Israeli Mozilla team is quite annoyed by Ubuntu users which (rightfully) want a “native” support for Hebrew as opposed to installing the xpi file themselves. Same for users which upgrade from feisty to newer versions and discover the support isn’t available any more.
Officially, the bug report is open for 3 weeks. But like Tomer, I do too remember an older report about this issue. I do hope to see the issue solved, as I’m (as a member of the debian-hebrew team) also getting questions about the package.
So, Ubuntu people – please help us get the long waited Hebrew localization for Thunderbird…