btracht Ysean2 on v4.3, SMS over SIP SIMPLE works out of the box for users within Kazoo (inbound and outbound). You might be able to make it work for external SMS with a carrier that supports SIP SIMPLE for SMS, but those are few and far between (VoIP.ms may, or at least I heard they did at one time.) I'm working on an integration add-on to remedy that, which will allow 4.3 to interface with HTTP SMS APIs,

but stock 4.3 only works over SIP.