You may have received an email with the following content:
The following proxy certificate is nearing expiration and must be signed again.
SaaS service: O365
Certificate common name: microsoftonline.com Expiry date: 26 May 2014
In order to optimize all applicable traffic, it is suggested that you re-sign this certificate in the Riverbed Cloud Portal. If you choose not to re-sign the certificate at this time, traffic for the hostname will be passed through.
If you log into the Cloud Portal, navigate to SaaS Platforms and select the appropriate platform (i.e.: O365), you will see the following screen: