Right now the person uploading the thread needs to be using gmail or a Google Apps account. We started there because there are 1.1 billion daily active users, b

Right now the person uploading the thread needs to be using gmail or a Google Apps account. We started there because there are 1.1 billion daily active users, but in the future it will work with other email service providers. Being able to use DKIM and SPF to authenticate threads is part of our value proposition, and a key part of the value proposition of email in general. (For example, being able to prove that you agreed on X project requirements with a certain person on a certain date.) Doing this type of authentication requires every message in a thread, not just the last one, so the most pragmatic way to meet this requirement is to work with email service providers with available APIs. The alternative is storing the entire contents of your inbox, but this doesn't make sense until we're ready to roll out our enterprise offering.