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:
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.