If you receive this message from your Zimbra server, then it is likely that an encrypted PDF or ZIP has been quarantined simply because the Zimbra virus scanner could not examine the contents of the file.
Great news! Zimbra Professional now includes Zimbra Archiving at no additional cost. The Zimbra Archive mailboxes will be available up to the same number of the licensed Zimbra mailboxes.
If you are running your Zimbra server in your office then it is recommended that your Zimbra server use the ISP for the office as a relay MTA. This tells Zimbra to relay all email direct to the ISP’s email server instead of attempting to deliver the email directly to the destination mail server. But what happens if your ISP implements a rule to require authentication for all relayed email? Well, you can configure Zimbra to automatically authenticate for you.