You need to register with your provider's BIS site as follows:
- Go to http://na.blackberry.com/eng/support/software/internet.jsp and find the link to your provider's BIS site
- Go to the BIS site on your computer and create an account
- Register your BlackBerry's PIN and whatever other information needed. With GSM devices from providers like Cingular and T-Mobile, you need to enter your IMEI number which is found on your BlackBerry under Options --> Status. You may need a different number for other devices, but that number should be on your Status screen.
- Now set up the email accounts you want forwarded to your BlackBerry
- For each account you set up, create a filter to NOT forward emails sent BY that email address to prevent emails you send from your BlackBerry from being forwarded back and showing up twice
- I strongly suggest NOT using the blackberry.net address that you're given with the account. It has no SPAM filtering, and there's no way to access the email other than on your BlackBerry.
- Do NOT attempt to connect to your company's email without checking with IT first. Some companies prohibit this kind of setup.