Hushmail would not protect you against the FBI grabbing an opened laptop a la the Silk Road Scenario, although if you registered for the service anonymously they would have protected your identity in that way.
Hush was one of the few remaining vendors to popularize PGP outside of the folks that actually worked at PGP (now owned by Symantec). This means that you can exchange secure messages with other PGP users by exchanging your public keys. While many PGP implementations have come and gone, Hush has endured and part of the reason is because it is so simple to use. There aren't any plug-ins to install and once you have changed your MX record, you literally have nothing to do.
If you want to send an encrypted message to someone outside the Hush ecosystem, you bring up the webmail client and attach a simple message password. (You have to communicate this password to your recipient via a text or phone call perhaps.) This feature, called Hushmail Express, has several additional options such as the ability to allow your recipients to create their own passphrase that can be used to decrypt all subsequent messages from you.
One place where Hush is showing its age is a 20MB limit on attachment size, and this could be a deal breaker especially when you consider that AppRiver has a 5GB limit on attachments. Business users have 10GB overall mailbox storage. Hush places a limit on 350 outgoing messages for the Web interface and 2,000 messages for the SMTP interface within any given 24 hours. This is to limit potential spam abuses.
Business users have access to a separate Web-based domain control panel. Here you can add new users, specify mail forwarding rules, maintain a common contact list for the domain, create white and blacklists, and specify things like a default mailbox size or setup a catch-all domain email address. These are only available to the domain administrator account, and are tucked away in the Preferences menu.
If PGP is important to you, then Hush is the only option among the products tested for an enterprise-wide deployment. And if you don't want the headache of managing a bunch of plug-ins, it has a lot of appeal. If your users spend a lot of time on their phones managing email, you probably want to look elsewhere for something that is specifically designed for phones or tablets.
Hushmail is priced per mailbox, with 50 mailboxes working out to $2,196 per year for 10GB of storage apiece. Pricing is very transparent, with additional fees for options such as domain admin, lost passphrase protection a step up to a 20GB mailbox and email archiving, each of which will cost $10 per domain per month.
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