Comment 8 for bug 145886

to avoid misunderstandings I'll try to clarify what's happening without using the word "upstream":

As described and discussed here: (https://answers.edge.launchpad.net/ubuntu/+question/13996) official mozilla builds of Thundebird (taken directly from Mozilla Thundebird website) are showing in every locale 5 options in the configuration wizard. As Wrwrwr said, some versions of Thunderbird packaged and included in Gutsy show only three or four options in the configuration wizard:

Ubuntu Gutsy locale packages showing 3 options:

en_GB
es_ES, es_MX
fr_FR, fr_CA
it_IT, it_CH

(example 1 (en_GB): http://launchpadlibrarian.net/9611260/en_GB.png)
(example 2 (it_IT): http://www.marco.boneff.ch/downloads/tb2-gutsy.jpg)

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Ubuntu Gutsy locale packages showing 4 options:

en_BW, en_HK, en_US, en_ZA
he_IL
hi_IN
zu_ZA

(example 1: (en_US):http://launchpadlibrarian.net/9611267/en_US.png)

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NOTE:

Every official Mozilla locale builds of Thunderbird 2.0.0.6 (binaries for generic GNU/linux systems, not specific .deb packages for gutsy) are showing 5 options during the configuration wizard:

(example 1: http://launchpadlibrarian.net/9611270/upstream.png)
(example 2: http://www.marco.boneff.ch/downloads/tb2-original.jpg)