I moved away from the corporate provider & things still work to the point of the SMS message arriving on the phone. It arrives - but the phone does nothing with it - i.e. it does not trigger a pickup. From what I can gather - this is because the email alert function of orange strips the message body of the message & only "alerts" the user of the email - this does not seem to be enough info to trigger a pickup!
Are you in the UK? Are you using orange email from www.orange.net with the alert function activated?