Postbox's latest update builds on the add-on functionality that was introduced in the previous beta, supporting Thunderbird's calendar plug-in Lightning, among others, and also comes with an announcement that the days of Postbox-for-free are coming to a end.
Postbox beta 14 for Windows and Mac has its own build of Lightning, which should allow users to communicate with both local and networked calendars. While Lightning works perfectly for me in Thunderbird, it wasn't able to talk to CNET's Microsoft Exchange server in Postbox. The Provider for Google Calendar plug-in, which gives users bi-directional Google Calendar access, works fine in Postbox--albeit with a slight hiccup when first loading the calendar.
Postbox now natively supports Gmail-style conversation threading and e-mail message counts. So if you've got a collapsed thread, where you can only see one message, there will now be a number next to it telling you how many unread messages are in the thread. Unfortunately, when I clicked on the first message, even if it had already been marked as read, it automatically marked all the unread messages in the thread as read, too.
There's a new Contacts sidebar, although the old Address Book is still available by hitting CTRL+2 or going through the Tools menu. The new Web services option, also available from the Tools menu or the Advanced Settings tab under Options, gives you more granular control over which Web services you're logged into through Postbox. This is useful if Postbox isn't your main Twitter manager, so you can keep your API count from exploding and preventing tweet updates.
Postbox Inc. also announced that they're expecting to take the program to a premium-only status in early September, when the program graduates from beta development. A single-user license will cost $39.95, with a family pack option consisting of licenses for five people living at the same address costing an additional $19.95. A lifetime upgrades option can be bought for another $24.95. These prices are currently discounted for a beta sale good until August 31, at $29.95, $9.95, and $19.95 respectively.
Postbox isn't the only Mozilla-based software to charge for downloading, but the list of programs that do isn't exactly long. Rafael Ebron, spokesman for Mozilla Messaging, pointed out that some of them include TuneUpTwitFactory.