One does not simply bypass steam guard (usually), You would have to confirm that your the owner via email
and I'm pretty sure the phisher just wants your account for spreading and not to change the email address in anyway.
You need to have the email of the account along with the password. Once you try and sign into the steam account a message will appear on the email asking if it was you trying to sign into the account and then a code following that you'd have to type in. The only other way I can see you bypass it is if you added another page to your phishing attempt and have them fill out there Email info and First and Last Name.