When you block a number on one Apple device, it blocks it on all Apple devices and apps. This includes the Phone app, the Messages app, the Facetime app, and yes, even the Mail app.
The Mail app was a surprise to me, since I didn't think that "Block a number" would include blocking any email addresses linked to that phone number in your Contacts app. But it does. (and annoyingly it sends those emails to Trash instead of to Spam)

