I sent a short message by email, and the other party (without email client) replied to me. The email interface shows "Free SMS", but I saw it online.

According to your description, after your mobile phone is successfully downloaded and registered, the SMS sent through the client is free. If the other party doesn't install the client, it's not a registered user of Yixin, but a point-to-point SMS that is normally returned to you by mobile phone. The normal phone number of the other party needs to be charged 0. 1 yuan/piece, which has nothing to do with you. If you need to pay the phone bill and handle general business, please log in to the online business hall of China (Anhui) Telecom. I hope my answer can help you and be adopted by you. Thank you for your concern and support for telecom products. Wish you a happy life!