So may groups have done it, from spies to terrorists to secret lovers. It works well. While providers might be constantly combing your drafts for ad suggestions or statistics (unlikely), what brings an email to someone's attention are one or both of the endpoints. I don't think that threats are often actively thinking of the IPs of webmail visitors as endpoints, or recording the order of access in an easy to digest or process manner.
They probably would be if you were targeted, though, but that's what Tor and VPNs are for.
They probably would be if you were targeted, though, but that's what Tor and VPNs are for.