It's good for people who don't want to tackle configuring and running a mail server.
If you demo it off a fresh ip you will hit inbox for a while but later the results will depend upon your senderscore and reputation. This data is compiled from FBL [Feed Back Loops] if done correctly.
You can license a copy of interspire, download the hack for or pay a coder to add dkim and ip add-ons. Don't forget to configure your spf zone files. Host at
datnog and they have an aol feedback loop enabled.
So you can run it yourself or try this service. That's my take at least.