[ Thanks to Amy
Kucharik for this link. ]
“The threats facing a Linux e-mail administrator with Windows
users aren’t any different than those facing someone using
Exchange, but the service opportunities are.“One important difference is the absence of per-client license
fees. Combined with a reasonable expectation that what you don’t
mess with will continue to work, this makes it possible to pass all
e-mail, in either direction, across the minimal number of servers
geographically necessary to serve your user…”