I am creating a chat application which requires that users be able to send and receive sms messages through a web interface. It would be somewhat similar to the text messaging service available in yahoo mail or in aol instant messenger. The situation is this: Given the high quantity of messages that would be sent and received, paying on a per message basis is not economically feasible. How is it that sites such as yahoo, aim, and twitter can send and receive unlimited sms messages?

Essentially, I am looking for a way to send and receive unlimited sms from my computer. Below is a list of some approaches I've come up with but have run into problems with as well. If just one of the approaches can be utilized effectively, then I am fine.

As a note on the nature of my application: I will only be sending messages to users that explicitly sign up for the service and permit the receiving of messages. They can unsubscribe at any time. This is to prevent spam.

• I am aware of software such as Kannel which allows one to connect to a providers smsc gateway. However, this adds the risk of not being approved by the provider which would be unacceptable. Is there any way to significantly mitigate this risk? Utilizing a gateway provider eliminates this risk, but adds the issue of per message pricing.

• I am also aware of email to sms. However, I have done some testing with that and it appears that this method results in many messages being undelivered or delivered VERY late. If it weren't for that, this approach would have been ideal. Is there any way to negotiate with carriers to remove me from their filters (considering the nature of my service as stated before)?

• I could use a gsm modem, but even with an "unilimited" plan on a sim card, there are still limits (around 100,000 messages or so). Furthermore, from my understanding, gsm modems are capable of only sending out around a dozen messages per minute. I need to be able to send out as much as several hundred messages per second. During the first 2 months, around 10 messages per second would suffice.

• There are ways to send out ads with messages to cover the per message costs. However, this is a deal-breaker since it has a high chance of tarnishing the quality of service. Furthermore, I know it is possible to do it without such ads since yahoo, aim, and twitter do not send ads with their messages.