There are several ways to 'spoof' who an email address is from. Its not hard to do. It sounds as if this is what has happened in this instance. There is nothing you can do to stop this sort of email being received using standard tools.
I have got a reply from Easily (who hold my domains) which says there is not a lot that can be done unless it comes from one of there customers. If your domains are with Easily then there is a good bet that they are.
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