and i think it is very easy to install a net-sniffer programm. you only need (for example) a root-server - lets say at strato - to sniff the network traffic inside strato and so the "man in the middle" is no problem.
Thats not the case at larger hosters, they all use vlans. The computer magazine C'T has tested it in their last server provider test and all tested providers use vlans to prevent net sniffing.
Maybe we can add some type of general setting that disables mail for all admin accounts if it is enabled in the server settings.