I have had the same problem too and the instructions below are not very clear. So here is what I have done on my phone to block an unwanted email coming to my phone. This also seems to work if you have set up Rules on your Mac for auto-replies (the function doesn't work if the emails are being bumped to your phone when your Mac powers down at home - seriously, seriously annoying).
Step one: I jot down the email address I want to block, or hold my finger on the email address, and choose copy. If the email address is already associated with a contact than see Steps A and B, below.
Step two: I open my "Contacts" app and press the "+" sign, which launches a "New Contact" page. On that page I type in an easily recognizable first name and type or paste the email address into the "+ add email" line. And save the contact.
Step three: Open the "Settings" app. Scroll down to the "FaceTime" line, and tap on FaceTime. At the bottom of the FaceTime page is the word "Blocked". Tap on the word "Blocked".
Step four: If you have blocked numbers or emails before you may see list of numbers or emails or both. Scroll down to the bottom of the list and find "Add New". Tap on "Add New".
Step five: Tapping on "Add New" will launch the "Contacts App". Look for the easily recognizable first name you used in Step two and tap on it. The "Blocked" page from "Settings" should relaunch and the easily recognizable first name you used should be on that list. You can check it is the correct email by tapping on the name.
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Step A: If the email address is already associated with a contact than delete the email from that contact. You will still receive texts, phone calls and FaceTime notifications, if you want too. I do not know why "Blocked" will not block emails in an already established contact, it just doesn't. So delete the email address and save the contact.
Step B: Tap the "+" sign to create a "New Contact". Follow Steps two through five.
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ALL BLOCK: If you want to block the texts, phone calls and FaceTime notifications as well, you can do this following the same steps, just look for the older contact entry and follow Steps three through five.