If you enable "Allow people to contact me through my profile (without showing my email address)" in your
Google Profile, people who find your profile can contact you. Google provides a contact form that sends all the messages to your main email address. "We've set some limits on how often messages can be sent and received, and you can disable the feature at any time by editing your profile and deselecting the checkbox,"
explains Google.
At the bottom of the email, Google shows an explanation:
"This message was sent to you from your Google profile. The sender does not have your email address. If you no longer wish to receive messages from your Google profile, you may edit your settings at
http://www.google.com/s2/profiles/me/editprofile".
{ via
GoogleWatchBlog }