Apple’s Hide My Email service lets users generate anonymous, randomized email addresses to help avoid spam, but it isn’t going to protect you from subpoenas — especially if you threaten the FBI directly.

Apple encryption and services can only protect you from so much

Apple encryption and services can only protect you from so much
End-to-end encryption ensures that your data remains yours on-device and in transit. This applies to things like iMessage and Apple Health, especially when Advanced Data Protection is turned on.
However, that doesn’t mean Apple won’t comply with a subpoena when it is presented with one that fits the scope of the request. Hide My Email might help protect users from spam, but if you’re emailing threats to the FBI director’s girlfriend, there’s nothing to protect you.