what 8 features tell you a document is a letter?

A letter is a written or printed message that contains important issues of concern and it is usually placed in an envelope and sent from one person to another. Letters may be informal (sent between friends and family members), or formal (official letter sent between institutions, businesses or government firms).
8 features that tell if a document is a letter are; if the document contain a date of when it was written,  an address of a house, dear sir/madam, paragraphs, first person, from or yours sincerely, if it is formal or informal and if it is written in past, present or future tense.  

An address of your houseA date of when you wrote itDear Sir/MadamFrom or Yours SincerelyParagraphsFirst PersonIt can be past, present or future tenseIt can be formal or informalHope it Helps. :)