What happens when someone new emails me?

It arrives in your inbox like any other message and you see who it is from, the subject and a preview line. Its formatting, images and attachments stay blocked until you decide, so nothing inside can load or track you. You can read the plain text before deciding if that helps.

Open it and the sender joins your contacts. Block them and, between DMCN inboxes, the block follows their key rather than the address they used.