As Mark points out, your post doesn't make a great deal of sense since IE9 is a web browser, not an email client. If you're using a web-based email service we'd need to know the name of the provider. If (instead of using your web browser) you're actually using an email client (such as one of those mentioned by Mark) we'd need to know which one.
However, I'll take a guess. The most frequently-reported problem relating to 'Bcc' going missing refers to Outlook Express (or similar email clients). It's resolved by simply going to the 'View' menu and clicking on 'All Headers'. Does that help?
Chris