Outbound mail is rate controlled based on IP address by the Barracuda Email Security Gateway as described in Rate Control Inbound. Rate Control for outbound email, however, can also be applied based on sender email address. If the number of recipients from a sender email address exceeds the specified Maximum Recipients per Sender over a 30 minute time period, the Barracuda Email Security Gateway will defer any further connection attempts from that particular sender until the next time frame. Deferred outbound messages will be logged as Rate Controlled in the Message Log.
Sender Based Rate Control, including specifying email addresses you wish to exempt, is configured on the BLOCK/ACCEPT > Rate Control page.