To better focus on Firefox and its other products, the Mozilla Foundation decided in 2012 to address the on-going stability of the open-source Thunderbird email client rather than new development, which was passed on to volunteer developers.

The rationale for the decision was that in view of the growing popularity of Web-based alternative forms of communications, Thunderbird was not likely to be a source of innovation and was seen more or less as a settled product with a basic set of features that users were happy with.

"Once again we’ve been asking the question: is Thunderbird a likely source of innovation and of leadership in today’s Internet life? Or is Thunderbird already pretty much what its users want and mostly needs some on-going maintenance?" wrote foundation chair Mitchell Baker in 2012.

Baker, who says she uses Thunderbird to organize vast parts of her life, now believes that the email client will thrive best if it does not rely on Mozilla for development resources and, in some cases, on Mozilla technology. "The current setting isn’t stable, and we should start actively looking into how we can transition in an orderly way to a future where Thunderbird and Firefox are un-coupled," she wrote in Mozilla's public governance forum on Monday.

Firefox and Thunderbird have lived with competing demands for some time now, with engineers working on Firefox, for example, uncertain as to whether and how much they should contribute to Thunderbird. "These competing demands are not good for either project," she added.

Many inside the foundation, including an overwhelming majority of its leadership, feel the need to focus on activities like Firefox that can have an industry-wide impact, Baker said. Thunderbird is not seen as playing such a role at Mozilla.

"Today Thunderbird developers spend much of their time responding to changes made in core Mozilla systems and technologies. At the same time, build, Firefox, and platform engineers continue to pay a tax to support Thunderbird," Baker wrote.

A Mozilla spokesman, who confirmed that the post was from Baker, did not immediately comment on whether the foundation was considering handing over the Thunderbird project to a group outside the organization.

In a follow-up post to that of Baker, the foundation's executive director Mark Surman wrote that it is talking to "at least one org who is considering supporting Thunderbird," besides looking at adding an user donation function, supplemented by the foundation's own assistance "in a small way," to support the Thunderbird community.

Baker wrote that she wanted to make sure that Thunderbird has the right kind of "legal and financial home" that will help the community thrive.