Unless they've somehow overlooked something, surely their terms of service will?

jfoster · on Dec 13, 2013

The terms of service are an agreement with their users, not with third parties who are emailing their users.

mcintyre1994 · on Dec 13, 2013

I see where you're coming from, and IANAL etc, but this surely must be a solved problem? For at least the last 15 years (longer?) we've had web mail where mail you send doesn't go directly to the user but via some other servers. If there is an actual issue here it's going to be a hell of a legal battle.