Cite an email as an in-text citation for APA style. The interviewee, a notation that this was a personal communication and the full date are needed for an APA in-text citation. For example: (C. Kane, personal communication, May 30, 2009). You can also cite the information directly in the text of the paper.
Cite emails in-text for MLA style with the author of the message in parentheses. For example: (Morris).
Cite the email on an MLA reference list with the author of the email, the subject line, the recipient, the date and the medium. For example: Andrews, Joyce. "Re: Pearl Harbor." Message to John Smith. 23 April 2003. E-mail.