Parts of a Letter of Request

I contain the information of the writer of the letter. What part of a letter of request am I?

I contain the information of the person the letter is addressed to. What part of a letter of request am I?

I am the greeting you see at the beginning of the letter. What part of the letter of request am I?

I contain all the information about your request. What part of a letter of request am I?

I contain the name and signature of the sender of the letter. What part of a letter of request am I?

I am used to end the letter politely. What part of a letter of request am I?