This is the new tactic. Long, randomly-generated "from" addresses. I think many e-mail systems nowadays verify the validity of the sending domain, so that means someone is registering these bogus domains. I've found the vast majority are from the set of newly-implemented top-level domains (TLDs) like .men or .loans. There are hundreds of these, and the bar for getting one registered is pretty low.
This is a real problem for spam filters. Many e-mail clients simply add the fully qualified "from" address to a blocked list when you click on the "mark as spam" button. That's worse than useless when each new spam message comes not only from a new address, but a whole new domain.
They're also getting clever about subtly mis-spelling words which might trigger a more in-depth spam filter. So even "learning" spam filter tools are being fooled. For now, blocking unusual TLDs seems to be the most effective way to limit the amount of spam which makes it through to me.
Oh, and once your address is on one spammer's list, it's on them all. They sell and share these lists. It costs them nothing to send out millions of e-mails, and there's no reason to ever purge or "unsubscribe" anyone from the list. Asking them to do so only proves you're receiving the spam, which makes your address even more valuable.