Even Windows 7 Home Premium version doesn't come with an e-mail client already installed.
Firefox/Thunderbird will run just fine on Win7 starter.
Or you can get the replacement for Outlook Express and install Windows Live Mail. It works just fine with POP3 and IMAP mail accounts.
Windows Live Essentials can also give you the Live versions of Photo Gallery, Movie Maker, Writer, Toolbar, Family Safety if you want those programs installed.