Why are my SMS messages taking years to send? But iMessages are perfectly fine?

So IIm texting my friend with iMessage ( we both have iPhones ) and I just started texting someone who doesn't have an iPhone and when I try to send them a message it ll take so long and it ll even say message failed it bugs like what the heck sprint.

Imessage uses Wi-Fi and texts use service network

It's most likely a problem with his telephone carrier or yours.