Google vs spam email

Industry groups have been working on authentication standards to prevent email impersonation since 2004.  Standards for sending and receiving domains help authenticate emails have come from the right sender.

In a blog post, Google has stated that the widespread adoption of these standards has dramatically reduced the ability of spammers to impersonate trusted domains.  Over 91% of all non-spam messages sent via Gmail is sent by authenticated senders who are using the standards.

Source: Google blog.