A messaging system configured to control collaboration and sharing of information between a sender, one or more receivers and an external service, comprising: a communications engine, comprising: a plurality of message interrogators to process a message (105,305) from a sender to a receiver, comprising: a message adjudicator configured to process message information (110,310); a message validator configured to allow or deny the message based upon the processed message information; characterized in that: the message comprises message information including message sender information and message content information, the message information further comprising sender information and message content information classification levels indicative of a person's privileges needed to view and access information; the message adjudicator is further configured to: obtain message information from an external service (171,172); compare message information from the sender with the obtained message information, the obtained message information comprising obtained message sender information, obtained message receiver information, and obtained message content information, and further comprising sender information, message content information and message receiver classification levels indicative of a person's privileges needed to view and access information; modify the message information from the sender to correspond to the classification level that is the higher of the message sender information from the sender or the obtained message sender information; modify the message information from the sender to correspond to the classification level that is the higher of the message content information from the sender or the obtained message content information; and filter the message content based upon the modified message information and the obtained message receiver information; and further characterised in that: the message validator is configured to allow or deny the message based upon the modified message information and the obtained message receiver information. a communications engine, comprising: a plurality of message interrogators to process a message (105,305) from a sender to a receiver, comprising: a message adjudicator configured to process message information (110,310); a message validator configured to allow or deny the message based upon the processed message information; characterized in that: a plurality of message interrogators to process a message (105,305) from a sender to a receiver, comprising: a message adjudicator configured to process message information (110,310); a message validator configured to allow or deny the message based upon the processed message information; a message adjudicator configured to process message information (110,310); a message validator configured to allow or deny the message based upon the processed message information; the message comprises message information including message sender information and message content information, the message information further comprising sender information and message content information classification levels indicative of a person's privileges needed to view and access information; the message adjudicator is further configured to: obtain message information from an external service (171,172); compare message information from the sender with the obtained message information, the obtained message information comprising obtained message sender information, obtained message receiver information, and obtained message content information, and further comprising sender information, message content information and message receiver classification levels indicative of a person's privileges needed to view and access information; modify the message information from the sender to correspond to the classification level that is the higher of the message sender information from the sender or the obtained message sender information; modify the message information from the sender to correspond to the classification level that is the higher of the message content information from the sender or the obtained message content information; and filter the message content based upon the modified message information and the obtained message receiver information; obtain message information from an external service (171,172); compare message information from the sender with the obtained message information, the obtained message information comprising obtained message sender information, obtained message receiver information, and obtained message content information, and further comprising sender information, message content information and message receiver classification levels indicative of a person's privileges needed to view and access information; modify the message information from the sender to correspond to the classification level that is the higher of the message sender information from the sender or the obtained message sender information; modify the message information from the sender to correspond to the classification level that is the higher of the message content information from the sender or the obtained message content information; and filter the message content based upon the modified message information and the obtained message receiver information; the message validator is configured to allow or deny the message based upon the modified message information and the obtained message receiver information.