And, what of Thunderbird 4? Mozilla’s skipped it in order to synchronize the releases of their web and email clients, which says that both products are now on an accelerated development path. Thereupon, here we are looking at the first whole-number Thunderbird release in 18 months — improved account wizard, tab handling, and Add-ons Manager.

Mozilla, version 4 be darned, has released Thunderbird 5 (release notes), which comes to market with a rather modest set of new features:

• More responsive and faster to start up and use
• Thunderbird is based on the new Mozilla Gecko 5 engine
• New Add-ons Manager
• Revised account creation wizard to improve email setup
• New Troubleshooting Information page
• Tabs can now be reordered and dragged to different windows
• Attachment sizes now displayed along with attachments
• Plugins can now be loaded in RSS feeds by default
• Over 390 platform fixes that improve speed, performance, stability and security
• Support for Mac 32/64 bit Universal builds (no longer supports PowerPC)

Get your very own copy Thunderbird 5 here (31.1MB).

The end is nigh? Nej…

For Mozilla, the PPC point of no return has been the introduction of Firefox 4 tech — lots of new features and too few users to justify the effort to port. Thereupon, Firefox, SeaMonkey and Thunderbird have all dropped PowerPC compatibility.

A measure of feature parity is available in TenFourFox, a private label build, which brings much of the goodness of Firefox 4 to the PowerPC platform.