“I can browse website, but why I can’t send & receive email using my Outlook Express?”
Website runs on Port 80, different from mail server which uses port 25 or 110. Browsing website means you are downloading data. Your ISP gives you different download and upload speed, it is not the same.
Well, sending out email is different from browsing website. You upload the data (or your mail) to the mail server for delivery.