iMessage log in
There's an email to me that someone used my Apple ID to log in on iMessage. I don't even use my iPhone now.
Question marked as
Welcome to the Apple Support Communities.
Apple would not send an email, they send a notification. See: Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support.
However, you can always review Check your Apple ID device list to see where you're signed in - Apple Support and If you think your Apple ID has been compromised - Apple Support.
Jack