The APA Manual 7th ed. indicates that personal communications include letters, memos, telephone conversations, some electronic communications (e.g., e-mail or messages from nonarchived discussion groups or electronic bulletin boards), etc. Basically, "works that cannot be recovered by readers" (APA Manual, Section 8.9, p. 260).
In the new edition, there is extensive discussion about citing "Traditional Knowledge or Oral Traditions of Indigenous Peoples" (pp. 260-261).
Personal communications do not appear in the reference list, but are cited within text as follows:
Narrative citation: J. Campbell (personal communication, October 13, 2019).
Parenthetical citation: (L. Brothen, personal communication, June 6, 2004).