The whole idea behind sending SMS (short message service) messages is in the name - you're sending a short message that you expect sent in a short amount of time. By using an SMS aggregator for mobile marketing you can send messages quickly, but it is important to choose the right aggregator. Not all providers, or aggregators, are of the same quality. 
Understanding the difference between good and bad aggregators means understanding the history of SMS, grey routes included. Check it out: