PayPal and eBay spam has gotten to the point that I’m not really sure how the actual companies send any legitimate emails anymore. I’ll pretty much automatically delete anything that purports to come from them, unless I’m expecting a payment from someone via PayPal.
Although Gmail has already taken some measures to protect users from eBay and PayPal scams, the latest will hopefully put this problem to bed. They’ve added an “authentication icon for verified senders” that displays a key icon next to the name of email senders that the service has verified as authentic.
How does it know that the mail is authentic? Brad Taylor of Gmail explains that “all of the sender's email is authenticated with DKIM,” which stands for DomainKeys Identified Mail. Right now, it’s a feature you enable from the Labs page under Settings, and is only in action on email from eBay and PayPal.