Easy to use, just send a verification request through their website or app, and they will reply within 24 hours to confirm. If you have any issues during the confirmation process, you can always reach them via live chat. We are using Verifykit for verifying our iOS apps' users. Currently, we don't have any issue running this service as well as receiving notifications when someone verifies an app. I like that they send push notifications to our customers when someone enters verification code in our app, so we are able to react faster.