Google, Yahoo tighten spam filtering

Google and Yahoo are expanding their use of a successful system for identifying spam.
The move is part of years-long effort to implement a series of checks designed to figure out if an email really has been sent by the domain it purports to come from.
Email spoofing has long been a problem since its easy to forge the "from" address, making it more likely the receiver will believe it came from a legitimate source.
By Nov. 2, Yahoo plans to being using DMARC (Domain-based Message Authentication,