Due to nasty bug in Gmail, warning about possible SPAM takes precedence over possible phising attack warning. Thus, if you receive an e-mail that is both phising attempt and is identified by Gmail as possible SPAM, then you will not see usual red warning, but a simple SPAM warning instead.
Here is an example screenshot:
It shows, that message has been identified as phising by Gmail, but the only indication of this is a changed context menu item and warning icon. There is no usual red-box-like warning, that always informs users, that serious troubles are potentially ahead.