What Causes Replies/Bounces to Unknown Email Messages to Show up in Your InBox

Due to the way that email works (specifically the SMTP protocol) it is possible for anyone to put anything they like in the "From:" field of emails that they send. This makes the email appear to be from someone else.

This is a fairly common practice among spammers in order to conceal their identity. There is, unfortunately, really very little that can be done about this. The email could be sent from literally any person using any mail server in the world. Tracking them down is extremely difficult and time consuming (if it is possible at all) and even if you do manage to track them down they are typically in foreign countries making any kind of legal remedy virtually impossible.

The problem is exasperated by the fact that there are many viruses that will take over an infected machine and randomly generate email using names and addresses found on the infected computer. All it takes is for someone, somewhere, who is infected by such a virus to have your email address in a document, address book, or email stored on their computer.

These virus generated "waves" of spam and fake emails tend to slow down over time and eventually fizzle out as those with infected computers either remove the virus or the virus does something to destroy all data on the machine that hosts it.

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