What is the reason why Unicom number can receive short messages but can't send them?

The reasons why Unicom can receive short messages but can't send them are as follows:

1. The number of the short message center is set incorrectly.

2. There is no signal or the battery of the mobile phone is low.

3. The system is busy during the peak period of holiday SMS sending. Try again later or avoid the peak period.

4. The sending format is incorrect. If you send a short message to PHS users, you need to add the area code before the number.

5. The sending time of the short message exceeds 24 hours.

6. The mobile phone blocks the short message sending function.

7. Being blacklisted by SMS.

8. The number balance is insufficient.

9. The cache of SMS application is full.

Extended information:

If the cache of the SMS application is full, the SMS may not be sent out. The solution and operation steps are as follows:

1. First, open the settings that come with the mobile phone.

2. You need to click more applications in the settings.

3. in application management, click to open the SMS application.

4. Then click Clear Data in the lower right corner.

5. click the clear cache function in the clear data.

6. Click the OK button to confirm clearing the cache again.

7. Finally, you can send short messages.