The latest steam client update introduced verified emails. What you do is go to File->Settings->Account tab and click Verify email address.

What happens now is that an email is sent to your contact address verifying you’re the owner of your steam account, and whenever information is changed on your account it first has to be verified through your contact email addy.

Now you can laugh in the face of all those phishers that were bothering you over steam chat. Though the sad bit is that the people that fall for it are probably the ones that don’t bother to verify their emails in the first place.