I have been working with Sigma for a long time and I am very satisfied. The setup and use of the service are quite simple, and the personal account is convenient. I really appreciate the ability to send newsletters through different channels, such as messengers, voice messages, and SMS. I especially like the cascading sending feature: first, the message is sent through the cheapest channel, and if it doesn't go through, it switches to a more expensive one. This ensures the message reaches the client and saves me money compared to sending only via SMS. The newsletters work reliably, and all messages are delivered without failures.
