Can I import my mobile phone SMS in Missive?
No. Missive offers no way to integrate with your existing phone number SMS messages. You need to use one of these third party services: Dialpad, Twilio, SignalWire. They are services that allow you to setup a new phone number to which you can receive and send SMS using custom programming or services like Missive. Their main use case are companies that want to offer customer support through SMS as an alternate channel beside email.
