Honestly, the first time I saw a Paypal email (something along the line of “check out your account activity”) I thought for sure that it was a phishing attempt. Not one link in their emails point to PayPal, they all point to stg like paypal-communications.com. You know, the type of domain name a phisher would come up with. Even the link talking about security doesn’t point to the PayPal website! That, and asking me to check my recent account activity when I know I haven’t used PayPal (and PayPal should also know that), is basically PayPal training their customers to fall for scams.
One of the reasons I think spammers have been so successful has to do with companies only.
Because companies send a LOT of spam emails / promotions etc that they have to come up with alternate domains to send emails. On customer side its very difficult to know the truth.