Your 'old' email address has been trawled or phished by somebody terribly clever, or by a hacking program. There are hundreds of them out there.
You should be able to set the spam filter parameters. For example, I had my email address trawled a couple of times, with the sender apparently being myself - very disconcerting. In the email app I use I set filter 'rules' so that any email from myself to myself got trapped. After a while the nuisance disappeared and hasn't resurfaced.
Update: another email purporting to have come from myself arrived today. What's interesting about it is that, after a delay of perhaps 3 seconds, the 'email' transformed itself into a pharmacy spam graphic and message promoting - you guessed it - sexual aids. I nuked the message. Instead I should have marked it 'junk' because because I want to trace its origins, assuming that can be done.