The sender isn't unknown, it will be in the headers of the email if you open them. I wouldn't worry too much, there obviously isn't an attachment which you clicked on otherwise you might have been in deep dodo.
Alienware 17 R4 2017 review
These brilliant Lego posters show just what children's imaginations are capable of
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Comment réinitialiser votre PC, ordinateur portable ou tablette Windows ?