Are bullets in mailboxes considered a threat?
sometimes yes sometimes no it depends if it was meant to hit it or just a missfire
What if someone pulls out a rifle in front of you and puts two bullets in it and fries is that consider a threat?
What is the largest number of mailboxes needed to hold 45 letters if each mailbox contains at least one letter and no two mailboxes contain the same number of letters?
It can be, if a reasonable man would perceive what you write as a threat. And such a threat can be prosecuted under the charge of assault, depending on the nature of the threat, and the ability to complete it. If this threat goes over the Internet, it can easily fall under Federal guidelines. In other words, potentially serious consequences here.