Some people have fixed email addresses, such as
[email protected] - this will have to be typed exactly to reach its destination.
Other people have emails in the format
[email protected] - in this case "anything" can literally be any combination of characters and it will reach the recipient regardless of spelling errors.
I suspect yours is the latter.
You could get a program such as Mailwasher, which lets you build up a 'whitelist' of allowable addresses - anything else would be flagged as possible spam.
There's not a lot you can do, unfortunately, except delete them.