after reordering our Interfaces, our Mailserver got out via the wrong IP via SMTP. (and gotten lots of missing reverse DNS Error replys) We have a Multipath rule that says that our Mailserver should go over a specific IP, but it didn't apply. [:(]
EDIT: think its based on our faulty multipath rule since we are using the sophos smtp proxy and i changed it to source: any. will test as soon as i can.