A mailbox with letters inside and a bird standing atop.

Mailbox With Letters And Standing Bird

A cardinal direction of an arrow pointing to a capital letter N, representing the North.

North Sign With Arrow

Lines representing text on a piece of paper in the style of a letter or assignment.

A street garbage bucket standing on two poles.

A speec bubble with three Z letters, indicating sleep.

An opened envelope with a letter coming from it.  

An open envelope with a pointing cursor and a letter with a notification icon on its top corner.

A busy and overworked manager or employee surrounded by charts, graphs, and notifications.