Can I delete my iMessage account?
Can I delete my iMessage account
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You can delete an AppleID, but not just an iMessage account. Deleting an AppleID deletes all accounts (iMessage, iCloud, FaceTime, App Store and purchase history, etc) and all data associated with the AppleID.
If you delete an AppleID you also can never reuse that email address as an AppleID.
See -> How to delete your Apple ID account - Apple Support