The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Turon Technologies:
Postboy is the ultimate email application. Postboy will download and compress all your email to your device and allow you to browse and search quickly while offline. NOW FREE - DOWNLOAD NOW! FEATURES: * Full text search of all your email * Find and read emails offline * Supports multiple email accounts * Perform email tasks without a network connection * Data mine hard-to-find emails on the go * Amazing compression allows years of emails to be stored in less than 99MB * Status page lets you know how much storage is being used * Supports loading and viewing of many attachment formats including: pdf, doc, rtf, ppt, xls, mp3, wav, aif, and mov REQUIREMENTS: * Supports IMAP, Gmail, Rackspace, and Google Apps email accounts FEEDBACK: Your feedback is appreciated. If you have any comments or issues, please visit our support site below, or email us at firstname.lastname@example.org. We read all reviews and respond to your suggestions with updates as soon as possible. Based on the reMail engine by Google. RELEASE NOTES: Ver. 1.0.2 (2010/5/25) Landscape mode Ver. 1.0.1 (2010/4/6) ++mp3,wav,aif,mov,ppt,xls,rtf Ver. 1.0 (2010/4/3) Initial version