In the public domain there is a program called Coyote. It serves to send SMS messages for free, but not through an e-mail analogue of your number, but through a real GSM gateway, which is registered in the program for each operator.
Coyote doesn't even need an installation, you just download a 2MB archive, unpack it into any folder in your file system and it's ready to go. Here is an incomplete list of supported operators for which direct SMS delivery is supported:
Russia (Akos, BaykalWestCom, Beeline, Centertelecom, Dalsvyaz, ETK, Megafon, Motiv, MTS, NCC, NTK, ON, Skylink, Smarts, Tatincom, Tele2, Utel, VolgaTelecom);
Ukraine (Beeline, Ecotel, GoldenTelecom, Jeans, Kyivstar, Life, UMC/MTS);
Belarus (Dialog, MTS, Velcom);
Uzbekistan (MTS, Unitel);
Moldova (IDC, Moldcell, Orange);
Czech Republic (O2, Vodafone);
Kyrgyzstan (Bitel, Fonex, Megacom);
some operators in Lithuania, Latvia, Germany (so far only 1 SMS per day).
The program has a number of additional functions that are very helpful in working with Coyote:
The only significant drawback is the appearance of the program, but considering that it is distributed with open source, you can change it yourself, having certain skills, to your taste. By the way, Coyote is available in Windows and Linux versions.
