The problem with secured mail alone is that often the metadata is all they need.  So, hushmail and other secured mail solutions are really a bad idea for anonymity, even though security may be fine.  They'll still know who you talked to and when, and that's often enough.

Everybody always get security mixed up with anonymity.  They aren't the same, and they require different solutions.

I use secretboxes.com, but layer it with my own encryption, tor, etc. because they have their own vulnerabilities.

I don't think there is a single standalone solution.  You need layers.