A box filled with junk mail.
Junk mail is defined as unwanted catalogs, advertisements, coupons and other offerings that are delivered to you via postal mail or email.
An email encouraging you to enter a sweepstakes is an example of junk mail.
advertisements, solicitations, etc. mailed in large quantities, usually by third-class mail
Third-class mail, such as advertisements, mailed indiscriminately in large quantities.
junk mail - Computer Definition