Why can’t I use a numeric-only Sender ID?

• Preventing caller ID spoofing
  Numeric-only Sender IDs are difficult to distinguish from real phone numbers, making them prone to misuse for impersonation.

• Compliance with regulations and carrier rules
  Many countries and carriers prohibit or strictly restrict freely assigned numeric Sender IDs.

• Avoiding delivery failures and quality issues
  Numeric-only Sender IDs are more likely to be rejected or filtered, leading to failed or delayed delivery.

• Ensuring traceability
  Alphanumeric Sender IDs, such as brand names, make the sender clearly identifiable, which helps protect recipients.

• Use an alphanumeric Sender ID (letters + numbers, maximum length depends on country/carrier)
  Examples: XOXZO, XOXZO_Notify, EZSMS

• Use a pre-registered short code or main number (pre-registration may be required depending on country and purpose)

• Use a brand name recognized by recipients (avoid misleading names)

Note: The allowed character set, length, and registration requirements vary by country and carrier.
Pre-approval or review may be required.

With the K Premium Service, which uses direct domestic carrier connections, you can use a pre-registered phone number as your Sender ID.
This allows recipients to call back the sender if needed.

Benefits:

• The sender’s number is clearly displayed, increasing trust.

• High delivery success rate and stable transmission through direct carrier routing.

For details, please see: What is the K Premium Service?

• 09012345678 (numeric-only: not allowed except with K Premium Service)

• 0120 (numeric-only: not allowed)

• X0XZ0 (misleading character substitutions: not recommended)

• VeryLongBrandNameOverLimit (exceeds allowed length: not allowed)

If a numeric-only Sender ID is specified, the request may fail validation or be rejected by the carrier, resulting in delivery failure.
In either case, this will negatively impact delivery quality, so please avoid using numeric-only Sender IDs.