Here is what Apple says will happen when you block on various apps:
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When someone is blocked in FaceTime, Messages or the Phone app, incoming calls will go directly to voicemail. They can even leave you a message that will silently show up in the Voicemail section of the Phone app, but hidden in a Blocked Messages section.

Messages or FaceTime calls won't show up on your Apple devices, and the person you blocked won't receive an alert or be any the wiser. They'll be left with the impression that you're ignoring them.

Blocking someone in the Mail app will result in their messages going to the trash folder for that respective email account.
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Notice that it says there is a hidden blocked voicemail section in the Phone app on the iPhone, so even though they leave a message, you don't ever have to see it.


On a Mac since 1984.
Currently: 24" M1 iMac, M2 Pro Mac mini with 27" BenQ monitor, M2 Macbook Air, MacOS 14.x; iPhones, iPods (yes, still) and iPads.