Why Meizu M8 mobile phone can't send text messages, but can receive them? Who knows why? Please give me some advice.

There are several possibilities: 1. You are using Unicom's number, and your mobile phone is out of service. You accidentally changed the number of the short message center, and then the short message can't be sent out anyway. The number of the SMS center is generally in the SMS settings, and the format is+8613800xxxxx, which can be found in the mobile phones of local friends or consulted in the business hall of the card used by the mobile phone.