What is the maximum length for an SMS sender ID?
If the SMS sender ID is alphanumeric, the maximum number of characters permitted is 11. If the sender ID is set as a numeric value, allowing the recipient to reply, then the maximum permitted number of digits is 15.
So there are two different sender ID maximum lengths, depending on whether you are using letters or numbers.
Why is there such a small limit on the number of characters permitted in a sender ID?
This is simply one of the SMS standards that has always been the case.
When SMS began, way back in 1992, the sender ID was set at 11 characters and has remained as the standard since then.
Back then, screen sizes were comparatively tiny, so it may not have been possible to fit more than 11 characters on all phone models.
Can you reply to a message if the sender ID contains letters?
If you set the sender ID to letters, recipients will not be able to reply to the text. (See example below where a message send was attempted and the sender ID of the incoming text was JohnLewis.)
So you have a choice. You can set the sender ID to letters, in which case you cannot reply to the message. Alternatively, you can set the sender ID as a reply number, allowing replies to be sent.
Can the SMS sender ID contain spaces?
The sender ID can only contain letters or numbers, spaces are not permitted.
No other GSM characters are permitted either. So no dashes or other imaginative ways to create visual interest!
Can the SMS sender ID contain a mixture of letters and numbers?
A sender ID can contain both letters and numbers. See below for an example SMS sender ID that contains both letters and numbers – Test1234. If numbers and letters are used, the maximum character limit is 11
Different countries and networks set their own rules on how much control they allow in setting the SMS sender ID.
Can the sender SMS sender ID be spoofed?
In many countries the sender ID can be set to whatever the sender wishes. This means that there is a danger that a fraudster could attempt to impersonate an organisation or individual.
There have been many illegal smishing campaigns that attempt to convince consumers to visit fake websites and enter their account details. (Smishing is similar to email phishing except the fraud is attempted over SMS.)
SMS smishing fraudsters will often use the sender ID to convince the recipient that the message is from a legitimate source.
Alarmingly if someone sends a text from a sender ID that is already a contact in your phone, rather than just displaying the digits of the number set, the person’s name will be displayed.
The message will also appear in the message thread, making it appear even more genuine.
Country restrictions on setting the SMS sender ID?
The ability to set the sender ID depends on which country you are sending to. In the UK, you have complete control over what you set it as. In many countries including the US, the networks do not permit you to send messages from a custom sender.
All messages must come from either a local long code (that looks like a normal mobile number) or from a short code.
Each country and network has its own rules on what is permitted.
If you attempt to send a message with a customised sender ID to a country or network that does not permit them, then the sender ID will usually be replaced with a local long code or the message may fail to be delivered.