SMS Server

I start working in a new project for setting up a server for sending (mainly) SMS. The requirements of the project are:

1. Send bulk SMS (one message - many recipients)
   
2. Send one-2-one SMS (one message - one recipient). This means a message that is personal to the recipient.
3. Delivery Reports
4. Ease of use any GSM provider that is cost effective. This is, use of local providers (by using a GSM modem and a SIM card) or use global providers through a TCP/IP connection.

For the project i am working on a Linux (Centos 4.4) machine that provides one serial RS-232 port for the connection of the GSM modem.

The applications used for sending SMS are the following:

1. Kannel (very reliable and provides delivery reports) - Provides web interface for sending
   
2. Playsms (a web-based gui for Kannel) - Provides web interface for sending
3. SMSLink - Provides web interface and desktop client for sending
   

The GSM modems tested up to now are:

1. Ericsson F251m
2. Wavecom Fastrack M1306
3. Some Nokia Symbian phones

All the GSM modems i used up to now can send SMS with no problem using any application, BUT the problem that i always have is that i never managed to get back a delivery report. And just to clarify what i mean "delivery report", when an SMS is been sent, the provider reports back to the modem "SENT" that means that the SMS is been accepted by the SMS Center, further the SMS Center forwards the message to the recipient and IF the recipient gets the message correct the SMS Center reports back to the modem that "SMS Delivered". This process is the usual delivery reports we always have with the mobile phones but this time it is crucial because if we send 1000 messages we need to know which of the customers delivered or not the SMS.
So the most reliable modem for this kind of project is the Wavecom (comparing the others available) and looking at the manual of the modem i can see that the delivery reports can be enabled by initializing the modem with a specific option, there is also an example in the manual showing what commands are needed to send an SMS and get back the delivery report but with the Wavecom modem i had in my lab this NEVER happened maybe because of a problem in the firmware of the modem and due to really bad support from the company i stooped trying with this.
The Ericsson by default is not sending back any delivery report and the Nokia phones are not designed for this kind of projects so they also abandoned.

So the status now is that i am still trying to find an appropriate GSM modem.