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Short Message Service:FAQ

Last Updated:Feb 29, 2024

This topic provides answers to some frequently asked questions (FAQ) about message delivery from the international site of the SMS console.

The SMS console states that the message has been sent. However, the message did not arrive at its destination. What can I do to fix this?

To troubleshoot the issue, perform the following operations:

  • If the destination cell phone has been powered on for a long time, restart the cell phone.

  • If the inbox is full, delete unnecessary messages.

  • If the destination cell phone has dual SIM card slots, you can swap the SIM cards.

  • Check if your mobile phone has security software installed, as it may block SMS messages.

If the issue persists, you can insert your SIM card into another cell phone and check whether the messages can be received.

I want to send messages to Vietnam. What message types are supported?

To ensure the delivery of OTP, messages sent to Vietnam are converted to text-to-speech calls.

What are the limitations and restrictions when I send messages to the US, France, and India?

When you send messages to US, France, and India, the following limitations and restrictions apply:

How many characters can be contained in a message?

A message can contain up to 1,500 characters.

What are the rules for setting a daily upper limit for message delivery?

When you set a daily upper limit, take note of the following items:

  • To ensure user experience, the number of messages that can be sent to the same mobile phone number each day cannot exceed a specified upper limit. The default upper limit is 20 messages per day.

  • You can set a custom upper limit but it cannot exceed 20 messages per day.

  • A day is defined as starting at 00:00:00 and ending at 23:59:59.

Why does ".0" appear after the verification code in an OTP message?

This is because the specified JSON object is not a string.

Can I send messages to multiple mobile phone numbers at a time?

You can send messages to multiple mobile phone numbers at a time by calling an API operation or using the SMS console.

Message flooding

Message flooding refers to sending a large number of messages to a group of mobile phone numbers in a short period of time by using malicious programs. This can be seen as harassment by the recipients and may also harm your brand and business. We recommend that you use the following methods to prevent message flooding:

  • Enable CAPTCHAs to prevent malicious programs from using your page to send messages. For example, the sender needs to enter a CAPTCHA to send a verification code.

  • Set the timeout period for receiving a verification code. In most cases, this period is set to 60 seconds, where the sender must wait at least 60 seconds between consecutive requests.

  • Set the validity period for entering a verification code. In most cases, each verification code is valid for 30 seconds. If you do not enter the verification code within 30 seconds, the verification code expires and you must request another verification code.

What are the possible causes for message delivery failures?

To troubleshoot the issue, perform the following operations:

  • Portability Failure: In most cases, messages can be received by a mobile phone number even if the carrier is changed. However, if the new carrier does not update network routing information in time, or if the mobile phone number has been transferred to the new network for less than 24 hours, messages may fail to be received.

  • Handset Cannot Receive SMS: A cell phone cannot receive messages as expected in the following scenarios: 1. The memory of the cell phone is full. 2. The cell phone is in airplane mode. 3. The cell phone is out of service.

  • Sending the Wrong Content: The message content is invalid. For example, a cell phone may fail to receive the messages that are written in unsupported languages.

  • Roaming: Message delivery may fail when the recipient is roaming. Whether a cell phone can receive messages depends on the roaming interconnection agreement among global carriers.

  • Carrier Spam Filters: Messages are filtered by carriers because the messages include keywords that may have been blocked by carriers.

How do I check whether a mobile phone number is valid?

To check whether a mobile phone number is valid, perform the following operation:

  • You can verify the validity of a mobile phone number based on the international dialing rules. However, this does not provide information on whether the mobile phone number exists, whether it is disabled, and whether its mobile network carrier has been changed.

If the specified mobile phone number fits the validity pattern, messages are sent. In this case, carriers charge you even if the mobile phone number does not exist and messages fail to be received.

Alibaba Cloud SMS can retrieve detailed information by updating the carrier route databases. In most cases, you are charged for this service.