Yahoo and eBay are joining forces to block phishing messages that specifically target PayPal users.
EBay and its PayPal subsidiary will use Yahoo's DomainKeys technology to force email senders to prove who they are.
DomainKeys works by verifying the domain of each email sender and the integrity of the messages sent.
Yahoo claims that the system is designed to stop false positives, where genuine emails are blocked accidentally.
"Once the domain can be verified, it can be compared to the domain used by the sender in the 'From' field of the message to detect forgeries," said a Yahoo statement.
"If it is a forgery, then it is spam or fraud and can be dropped without impact to the user."
Once a mail sender is verified as genuine, the system can be used to create a 'persistent reputation profile' which acts like a white-list in anti-spam policies and allows email from that source.
Yahoo said that these lists could be shared between service providers and even exposed to the user.
John Kremer, vice president of Yahoo Mail, described the system as a big step forward for consumers in defence against the bad guys.
Security vendor GrIDsure maintained that banks and credit card companies had to do more to protect customers from fraud.
A survey released today by GrIDsure found that most financial institutions believe that simply giving customers their money back is enough in terms of 'fraud protection'.
However, 83.2 per cent of those surveyed said that the experience would still leave them feeling 'violated', and just over half would consider closing an account from which money had been stolen.
