In 2007, the Mozilla Foundation separated from his work email in a subsidiary called Mozilla Messaging. The objective was to develop and Thunderbird email applications using the Mozilla bird (Eudora, etc.) without impacting the development of Firefox.
But with the development of webmail and similar services like social networks, the Mozilla Foundation has developed plug-ins for Firefox on electronic mail in webmail and social networks as part of Mozilla Labs.
The Mozilla Foundation has decided to return to Mozilla Messaging and teams from the old structure with those of Mozilla Labs. Thus, the Mozilla Messaging team will help those from Mozilla Labs to develop functionality around email while teams from Mozilla Labs will enable the Mozilla Messaging to develop a modern version of Thunderbird.
The development of Thunderbird, Mozilla Messaging integration in the Mozilla Foundation will not affect current developments (Thunderbird 3.1.x and 3.3 alpha)