Did you try this?
http://playground.arduino.cc/Code/Email
You may have problems with it also. It sends email like an email server sends to another email server. The problem may be your email will be rejected because your ip address is not in a commercial subnet. If your account with your ISP is a residential type and your IP is issued by dhcp, then it will probably be rejected by many public email servers like Gmail and Yahoo.
Since the ethernet library does not support SSL or TLS, you can't send email to either of those services as a client.