Enkive is an Open Source email archiving and e-discovery software. you can download it, and enjoy all the goodness of an Affero GPL licensed software.
You Are in Control
Enkive will run on your premise or in the cloud. You get to decide how comfortable you are with storing organizational communications in the cloud or how compelled you are to self host; and changing your mind is not a major issue.
No Back doors
Some organizations outsource their email archiving to 'cloud' services. For some, this is a suitable option. But do be careful. Any email you save may be subject to requests by governments. If you use the Cloud, be aware that certain government authorities may be able to obtain copies of your email without even telling you. In fact, US law prohibits Cloud service provides from even telling you that they have received or fulfilled a request for your data.
Enkive's modern technology using no-sql data base and indri search engine means that the application will run fast and will scale.