I'm working with a small business that uses SMS to communicate with their customers. At the moment we send about 20k messages per month. Today this is done by syncing all phone numbers to an iPhone in groups of 50 and then sending the message to each group one at the time. Today it's a very manual process and we'd like to make it more automatic. Unfortunately, when we calculate ROI for something like Twilio it's still not worth it money-wise. And today I found smstools! It made me very excited except for some concerns regarding performance. The text messages that are sent are always multi-part and each sendout may be to a few 1000 numbers also preferably we'd only use one, or maybe max 2 numbers which limits us to to max two modems.
How high performance have you been able to reach? I.e. how many messages per minute? What modem(s) are you using? Which one(s) are the best for high performance? What are your use cases? Anything else I should know before trying this out for our use case?