As personal communication is not recoverable or archived, it is not included in a reference list, but is acknowledged in-text. Personal communication might include private letters, tutor comments, your own class notes, interviews, telephone conversations, social media, etc. Use the initials and surname of the person with whom you corresponded and as exact a date as possible.
Examples
In-text citations
Narrative
K. W. Wiremu (personal communication, January 18, 2010) commented that...
Parenthetical
...(K.W. Wiremu, personal communication, January 18, 2010).