Yesterday Google reported an issue with legitimate messages being Quarantined in Postini. Google is now reporting that the issue is resolved.
"A copy of the quarantined messages will start to be reprocessed in the next hour. Engineers will start to redeliver messages in small batches. It's then expected that it will take several hours until all messages are reprocessed.
Messages unaffected by the original issue and already properly classified as spam will not be reprocessed. A new copy of the affected messages will go through a full regular Postini scan using proper customer configuration settings and filters, as present at the time of the issue. Reprocessed messages that are still considered as spam will be placed in quarantine again, creating a duplicate entry in the quarantine. The process will not clear out the Postini quarantine of affected message copies; message copies already quarantined will remain quarantined."
Check the Google Apps Status Dashboard for more information at http://www.google.com/appsstatus