Hello Cedric,
I did a quick check across the common blacklists, and seems none of them has blacklisted you. As for Senderbase, (which is not a blacklist as it only scores sender IPs and -ranges), your current score is slightly negative, so make sure to have an eye on the traffic that goes trough your Email Security Appliance's, as you are most likely sending spam. Thus, make sure you configure you listeners and HAT to accept outbound traffic (emails from internal to the Internet) only from selected hosts, and not your whole intranet IP range. Otherwise, infected PCs would be able to send spam trough your public IP.
Hope that helps,
Andreas
