Email is supposed to go from the sender's machine to the receiver's machine. That's how it should work by default, that's how TLS connections makes the communication vaguely secure, and that's how it makes it difficult for powerful third parties to have a peek at everyone's communications.

As far as I know, Gmail accounts are only a subpoena away from the US government. But a sheeva plug (or R-Pi) hosted at my home? They need a warrant. Even for countries that don't need warrants, wire-tapping everyone is expensive: it must be done one home at a time.

Now maybe the botnet situation is so bad that it is worth sacrificing our ability to send e-mail. Still, this strikes me as the wrong solution. Blocking outgoing 25 by default is fine, but we need to be able to lift the restriction if we want.