Personal notes, e-mails, conversations, lecture notes etc. that is not available to others, should be referred to as communication.
Name the person cited and if necessary working place. Give information as to why you are citing this person, that this is an e-mail, and the date of the e-mail. Make sure you ask the person in question if you may cite him/her and if you are citing them correctly.
… A. Hansen, conversation, March 18th, 2017.
Anne Hansen, conversation, March 18th, 2017 wrote in an e-mail that …
Anne Hansen, lecture note, March 19th, 2017 said in a lecture that …
Do not include
May be added as Personal communication to save invormation.