AMA Style: The Basics for Pharmacy Writing: Emails or Conversations

Note:  Also known as "personal communication."  The AMA Manual of Style says to NOT include personal communication in your reference list. AMA style only permits inclusion of personal communication in your text. Permission from the author is required, and oral communication should be supported in writing.

Example (see additional examples in the manual, in Chapter 3, section 3.13.10)
 
According to an email from local pharmacist J.F. Addison, PharmD, in July 2020....