We had some trouble with the installation, mainly because the software version has German instructions and installs the German version of .Net Framework. Once installed though, the menus and commands are in English. Tutanota is based in Germany, which could be important for customers concerned about American email privacy.
One of the distinguishing features is that its zero knowledge encryption process hides the message subject. Most of its competitors still send this information in the clear.
Its webmailer is the simplest of the bunch with bare-bones features. You can select whether a message is going to be sent encrypted or not, and if the former you can choose a passphrase for your recipients who aren't in the system to read and reply to your messages. This passphrase can be sent via a text message, in which case Tutanota picks up this information from your Outlook address book. That is a pretty clean way to do this.
Speaking of which, if you want to make use of the Outlook plug-in, you need to use IMAP with Outlook 2013 (but not POP). If you use Exchange, either Outlook 2010 or 2013 is supported.
For the Silk Road scenario: if you don't save a mailbox password when you login, you might be able to thwart this if you can quickly close Outlook before your laptop is seized.
Tutanota still has some rough edges, but as a client-oriented product it has a lot to offer, and as the product matures this could be a worthwhile choice for a limited encryption roll-out in your company.
Tutanota has a 1GB mailbox storage size limitation and is priced at 2 euros per user per month. It is limited to 25MB attachments.
Virtru has a nice balance of plug-ins and mobile apps that support its easy-to-use encryption operations across a variety of email circumstances. If you use Windows Outlook 2010 or 2013, you can encrypt messages on any SMTP-based email server. If you make use of Google, Yahoo or Outlook.com webmail, you can run either their Chrome or Firefox browser extension on any Windows, Mac or Linux computer. And there are mobile apps that support iOS and Android phones too.
You can also install an app for your Google Apps domain. The Google Apps support is somewhat unique in that it adds primitive data leak detection for your outgoing messages. You can have it recognize credit card or Social Security numbers, for example, and have it either warn you or automatically encrypt your message. This is all set up in a separate Web-based admin portal. There are other options located on this portal too: you can set expiration dates for messages, track who is being sent encrypted messages, search for files, and set other security policies.
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