Short messaging service is another name for text messaging. Cellular carriers use a complex network of computers to transmit text messages and voice data both internally and between other carriers. When the text message recipient has issues receiving the message, you may receive an SMS termination denied error.
SMS is split up into two separate features. SMS origination allows the phone to send text messages to other devices. SMS termination allows the device to receive text messages. The phone can send but not receive, or vice versa. When you send a text message to a phone that doesn't have text messaging capabilities, the carrier's system will send the "SMS Termination Denied" message to your phone to alert you the message wasn't received.
Account Related Causes
Most carriers charge per text message unless the account holder opts for a separate text messaging feature, or the rate plan includes unlimited text messages. Some people opt to remove text messaging capabilities from their account to avoid running up their bill. Some carriers offer the ability to block text messages from specific numbers. For example, if you don't want your child to receive text messages from a certain number, you can block the text messages from that number only.
System Related Causes
If the network breaks down, you have an outage. Outages usually affect many customers at once. They can affect customers from specific regions, or all of the carrier's customers at the same time. Text messages are carried over voice channels, so if you can't send or receive calls, you can't send or receive text messages. You can still receive data if your text messaging isn't working. If you have multiple phones that are receiving the SMS termination denied message, contact your carrier to find out if there is an outage.
User Related Causes
Text messages have a limit of 160 characters, including spaces. If you type a message that is longer than 160 characters, some phones will automatically convert the text to a picture message. Others will break the text into multiple parts. Older phones will simply give you an error telling you to reduce the length of the message. This feature is dependent on the phone hardware and the carrier's network. If your carrier's network doesn't support it, you'll get an "SMS Termination Denied" error.