I have a BB Pearl and we've had Telus' Email/IM plan on it. Everything worked great. While we were on vacation a couple of weeks ago, I added on web service as well so I could keep in touch while we were gone. When we got home I cancelled that and went back to just Email/IM again. IM works fine, but I haven't been able to send or receive email (BB address) since. When I try to send a test email from home, it comes back undeliverable.
The majority of new members have no idea where that is, so you need to be specific. Go to e-mail options or settings, select service books and hit resend...
If re sending your service books ( from the email settings icon on your device or from the webpage) does not work, call your carrier to ensure you are provisioned correctly.