Yesterday Mozilla.org released version 1.6 of their browser suite.
This release brings a lot of improvements to the Mail component, cross-platform NTLM authentication, a lot of security bug fixes and other bug fixes.
More details here:
Mozilla 1.6 Release Notes
MozillaNews
and probably MozillaZine as well, but their site was down at the moment of writing.
This means that Mozilla Firebird 0.8 will be released shortly, but a few bugs are still open.