Postbox 3 now supports Gestures for those using Lion with a trackpad or other device that supports multitouch gestures.  Settings must be changed within Postbox and System Preferences to enable this feature.

Changes within Postbox

To configure the actions for three finger swipes left and right, go to Preferences | Advanced and then configure the individual actions for each swipe:

In addition to left and right gestures, Postbox always supports pinching in to zoom in on a message and pinch out to zoom out.

System Preferences

Trackpad:

• Within System Preferences, select Trackpad / More Gestures
• Make sure that the setting Swipe between pages is set to "Swipe with two or three fingers"
• Set Swipe between full-screen apps to "Swipe left or right with four fingers"

Mighty Mouse:

• Within System Preferences, select Mouse / More Gestures
• Set Swipe between pages to "Swipe with one or two fingers"
• Deselect the checkbox for Swipe between full-screen apps