This app is almost interactive. The mail appears to be coming towards you, inviting you to grab it. With this interactive feature, you may be more likely to touch the app, leading you to the business. The simple red and blue checkered envelope creates a elegant pattern and consistency.
Statistics app icon by Edward Northwood, via Behance
From this icon you can easily tell what it is for, dream journal. The journal itself is nicely done in being detailed and including such things like a page marker. You can tell it is a dream journal because of the added moon