All Barracuda Spam Firewalls.
If your Barracuda Spam Firewall's Basic > Message Log page shows the Action of Allowed or Whitelist and Delivery Status of Rejected for a particular message, this means the destination mail server rejected the message after the Barracuda allowed it. Please check your mail server's SMTP logs for any error messages. The actual SMTP error code that the mail server returned should be present in the Delivery Detail field in the Message Log of your Barracuda Spam Firewall and may help you determine why your mail server blocked the message.
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