Infrastructure for sending a large number of SMS from the server?

Question

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Hi friends.
I have long been interested in the question of sending messages from the server to a phone number.
How to do this is understandable, I implemented it literally in a week (sms.ru)
This is what interests me:
There are such powerful projects as Vk.com and Telegram.
- how do they send these same messages? Not sms.ru they use something.
- high speed of delivery, sending to any phone numbers
- who do you need to conclude contracts with? With all network companies in the world?
Who knows the answers - tell me.
This question is of interest to many developers nowadays - it’s convenient.
Sincerely.

Answer 1

Depends on where to send. If in Russia / Ukraine, then the main ones are enough - Beeline / MTS / Megafon / and even one of them. If you need to go abroad, then negotiate with local operators

Answer 2

There are various web services. I personally use this. Paid, but transparent API.
www.websms.by

Answer 3

www.bytehand.com - I've been working with them for a year, no problems. API clear