Great, but not invulnerable

Positive Review by crazypens30
about SIGAINT Aug 2016

I've used Sigaint before, and while they do make every effort to preserve your privacy and not reveal your identity, it has been the target of attacks before. If you read this article from VICE: After Hacks A Dark Web Email Provider Says A Government Spied On Its Users, it goes into a bit more detail about it.

That aside, it's still a more private email provider than some of its clearnet contemporaries, and at the very least, its admins do make an effort to counteract hacks and other such intrusions. And I think they've made even more improvements since these attacks have occurred.

It's not perfect, however - some of the organization features you might expect from a clearnet email provider (like Gmail) aren't available yet. They might have something like that in the future.