Personal communications that are inaccessible to your reader (interviews that you've conducted, e-mail messages or letters you've received, etc.) should not be cited in your reference list. Instead, give an in-text citation only that provides the initial(s) and last name of the communicator and the date of the communication:
J. Smith (personal communication, November 18, 2016) stated that the server had crashed several hours ago.
See Publication Manual, 8.9 and 9.37.