This applies to F-Secure Internet Gatekeeper 6.60. There is a bug in F-Secure Internet Gatekeeper which may result to the following error message when releasing messages from quarantine: Sender: <> Recipient: “Example Recipient” Subject: DELIVERY FAILURE: User test.user (test.user@example.com) not listed Message ID: Spool ID: smtp22031972 Reason: message stopped or processing completed with errors, check ‘failure’ records in mail log The message then gets quarantined again. If you encounter these errors for no apparent reason, please check whether you have defined the “Max Number of Recipients per Message” setting as zero, which should set it as unlimited. In centrally managed environments the setting is located at F-Secure Anti-Virus for Internet Mail / Settings / Inbound Mail (as well as Outbound Mail) / Receiving. If the setting has been set as zero (0), releasing the messages from quarantine