[posguy]

Have you considered using T-Mobile's WebDigits ( https://webdigits.t-mobile.com ), AT&T NumberSync for computer or whatever Verizon and other carriers have to offer for handling SMS on a computer perchance?

You could also use multiple phone numbers to send SMS to avoid SMS ratelimiting. FYI most carriers consider Person to Person messaging to be below 1 message per minute and run between 40% inbound to 60% inbound messages.

One thing to watch out for is some carriers like Cellcom if I recall sell unlimited texting plans that actually have a 20,000 message cap then $0.01 per message thereafter. A cousin of mine hit this about a decade ago as she was part of many MMS groups.

[lukeasch21]

Those look like interesting options, and they're surely be more reliable than relying on the phone's own SMS capabilities, but I wasn't able to find a public API for any of those services. As far as SMS rate limiting goes, I agree that multiple numbers would be good. Perhaps if there's a demand for it, I can create a feature that switches numbers from the database on the fly as it notices some are hung up.

>FYI most carriers consider Person to Person messaging to be below 1 message per minute and run between 40% inbound to 60% inbound messages.

Yep, I've read into that a little. I wasn't able to find anything explicitly forbidding a service like this in their terms, although there's a lot of legal documents that carriers have so I could have missed it. I read that you should expect about 1 SMS/second on consumer carriers, but it seems like I'm able to get about 2-3 SMS/second in my testing.

I didn't know about carriers having an unlimited SMS threshold... I'll have to look into that, thanks for the heads up!

[posguy]

Yeah, neither WebDigits nor other carrier offered services seem to offer a public API, it would be a matter of reverse engineering their website :c

[shanebellone]

SMS is limited to 1 message per 3-6 seconds. The modem incidentally limits throughput.

Also, Google Fi has unlimited text/call for $20/m. Their SIM does work with USB GSM modems.

[posguy]

GSM is not available on AT&T or Verizon and T-Mobile is ending GSM support in under a year. Right now T-Mobile's GSM is running in a 200Khz carrier in the guard bands of LTE, making it perform worse due to the narrow bandwidth which means your allocated fewer timeslots which limits message throughput, and interference from the LTE carrier directly beside it degrades signal quality as well.

Nevermind most GSM stacks crash when receiving/sending many messages quickly, they aren't designed for high throughput messaging.

Sending via a carrier's multi-device calling/texting option where you bypass their cell network and connect to their servers over the web, or using VoLTE or VoNR is going to perform much better than GSM