As the social-networking e-mail client Postbox approaches its announced general release date at the beginning of September, the cross-platform program updates with what looks to be more a "tidying-up" release. Available for Windows and Mac, Postbox 1.0 beta 15 introduces a new version of the Thunderbird calendar plug-in Lightning, improved contact searching, and other performance tweaks--but not much else.
Derived from Mozilla Thunderbird, Postbox beta 15 will also let you drag and drop e-mails from one account to another and introduces a crash reporter that had been strangely missing until now. Search queries that return no results will now suggest alternative search terms, and more plug-ins have been ported over from Thunderbird, including ThunderBrowse, Virtual Identities, and support for Mozilla-client profile rescuer MozBackup. Frustratingly, Postbox now requires a reboot to work--at least, it did on upgrading my installation from beta 14.
The full changelog can be read here.