This sort of thing is a well known ploy by spammers to get unsuspecting users to open the email to read it.

It's happened to me as well. The spammers create millions upon millions of spam emails a day using an email address generator. The generator creates email addresses that may or may not be genuine, and any that are not are simply discarded if and when they are returned from the ISP because the address is not known.

But by creating so many they are bound to "strike lucky", and then if the receiver opens the email, certain cleverly crafted emails can send a message back to the spammer to say they have found a genuine email address.

You seem to be aware of the risk of opening such emails, and that is a great start. One thing I would ask, although you know not to open any such emails, does your OE have its Preview Pane open? If so, by highlighting such emails to right click and check the message source, you may be previewing it, and that is as good as opening it.

If you don't then that is even better.

There is little you can do about it, and eventually those type of emails will die off. In the meantime, if you don't send many emails yourself, you could set up a message rule in OE's Account options to move any more you receive either directly to Trash, or to a special folder where you can check them periodically.

I hope that helps.