Apple's 4S mobile phone can't send text messages. What happened?

1 SMS center number error: SMS center settings are different in different regions. Please call the local operator for customer service consultation.

2. Poor cell phone signal: the signal in the user's area is unstable, and there is no network for the time being, so it can only be sent to a place with good signal.

Mobile phone inbox is full: check whether the mailbox is full and clean it up.

4 the quality problem of the mobile phone itself: this phenomenon is unlikely to happen, but it still exists and can only be solved after sale.

5. Set the blacklist function of mobile phone: This will cause some people's short messages not to be received, so you need to turn off the blacklist function of mobile phone and restart the mobile phone.