How to stop junk emails coming from someone posing as a contact?

Check here -> Recognize and avoid phishing messages, phony support calls, and other scams

Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

• If you receive a suspicious email or SMS text message that looks like it's supposed to be from Apple, please email it to reportphishing@apple.com

• To report illegal, obnoxious, unwanted or malicious e-mail from an Outlook.com, Hotmail, Live or MSN account, please forward the unwanted message in its entirety (including the entire message header), to abuse@outlook.com

• To report illegal, obnoxious, unwanted or malicious e-mail from Gmail -> https://support.google.com/a/answer/178266?hl=en