The essence of the problem:
To notify registered users of the service about an event in the service events.
Periodicity — a day for ten pieces, about the mass mailing is not out of the question!
It is possible to send the message through the EMAIL2SMS gateways of cellular operators, but in reality works only gateway Megaphone.
I would like to know the gateways of other operators on codes def. You can PM.
The option of using an external service for sending via HTTP GET/POST is also considered.
I would like free but will be considered a commercial option, but for a physical person.
PS the Option of using a GSM modem — not frequently, for hosting on a remote site(in another city).
PPS Search in Google and Yandex returned multiple gateways EMAIL2SMS, but as I wrote above work out of them, only Megafonovsky, and therefore need relevant and reliable information.