Are these messages coming through eBay? Is this anything to do with eBay?
Hopefully these are just typical "phishing" scam emails, which you ignore or preferably delete unread.
However it's possible that you have unknowingly downloaded some malware, possibly from clicking on one of the very dubious banner ads that try to frequesnt eBay. If so, you may need anytimalware protection, e.g. malwarebytes antimalware.
