I use an app called MailTones in the iTunes app store... it works by forwarding your email to them - they send it back with a custom alert (from their list). It's not the most secure way to handle it, but the only non-JB way I have found...
Originally Posted by dochill4u
In my case, I get an email with a problem report number only (8 digit number ONLY), so I am not concerned about the security issue, but you may be.
It does work well, and is extremely reliable. If the security thing is not an issue for you, I highly recommend it.
It won't "ring" when on vibrate, but there is a way to set all alerts for email accounts to nothing... except the one(s) you are interested in - so you don't need to switch to vibrate mode.