How to send SMS to mobile number for authentication that too by making use of Portals

One common way to achieve the scenario you described is to use an SMS API to send the OTP to the user's mobile number and verify it on the backend before allowing the user to submit the form. Here's a high-level overview of the process:

1. The user fills out the form and provides their mobile number
2. The backend generates an OTP and sends it to the user via the SMS API
3. The user inputs the OTP they received on their phone into the form
4. The backend verifies the OTP and if it's correct, allows the form to be submitted.

There are many SMS APIs available that you can use to implement this, including Twilio, Nexmo, and many others. You can choose one that fits your requirements and budget.

Source: Bulk SMS Service Provider

One common way to achieve the scenario you described is to use an SMS API to send the OTP to the user's mobile number and verify it on the backend before allowing the user to submit the form. Here's a high-level overview of the process:

1. The user fills out the form and provides their mobile number
2. The backend generates an OTP and sends it to the user via the SMS API
3. The user inputs the OTP they received on their phone into the form
4. The backend verifies the OTP and if it's correct, allows the form to be submitted.

There are many SMS APIs available that you can use to implement this, including Twilio, Nexmo, and many others. You can choose one that fits your requirements and budget.

Source: Bulk SMS Service Provider