I keep getting reminders to subscribe to the iCloud service, but read my words: I do not want iCloud! Is it possible to deactivate these annoying reminders? (I'm on Mac OS El Capitan 10.11.6).
Go to Apple ID and unchecking these items (if they were be selected):
In general, every message from Apple has an unsubscribe link, usually, at the end of a letter. Plesase, check it.
Finally, check out a message sender in your Mail app, perhaps, those messages are not from Apple, and they are just a spam.