Sinch SMS

The sinch plugin sends text messages to your users through your own Sinch account. It sends phone number verification codes, codes for sensitive actions such as withdrawals and password resets, and a message when a deposit or withdrawal completes.

warning

Unlike the AWS SNS, Telnyx and Messente plugins, the Sinch plugin does not treat the phone number as a login credential. A signed-in user can replace the number on their account with a new one by confirming an SMS code alone, with no email confirmation or 2FA code. It doesn't check whether the number is already verified on another account, and it sends deposit and withdrawal SMS to any valid number on the account, verified or not. If your users rely on SMS codes to protect withdrawals or password resets, choose one of the other three SMS plugins. See Compare the SMS plugins.

What you need

• The Enterprise plan on HollaEx Cloud.
• A Sinch account with an SMS service plan. Sinch bills you directly for the messages you send.
• A sender: a phone number in international (E.164) format such as +15555550123, a short code, or a sender ID that is allowed in the countries you send to.
• No other SMS plugin installed. Only one can run at a time.

Set it up

1. Get your Sinch details. In the Sinch Customer Dashboard, go to SMS → APIs and copy the Service Plan ID and API Token of your service plan. Note which region the service plan is in.

2. Install the plugin. Go to Operator Controls → Exchange → Plugins, find sinch under Available to install and click Install.

3. Configure it. Click Configure on the plugin, fill in the settings below and save.

   Setting	What it does
   servicePlanId	Required. Your Sinch SMS service plan ID.
   apiToken	Secret, required. Your Sinch SMS API token.
   fromNumber	Required. The number or short code messages are sent from.
   region	The region of your service plan: us, eu, au, br or ca. Default: us.
   send_sms_deposit	Send an SMS when a deposit completes. Default: on.
   send_sms_withdrawal	Send an SMS when a withdrawal completes. Default: on.
   send_sms_user_verification	Send codes for actions such as withdrawals and password resets by SMS to users who chose SMS for their codes. Default: on.

4. Test it. Sign in to your exchange as a test user, add a phone number and confirm it. Then make a small deposit and check that the SMS arrives.

What your users see

• Phone verification. A user enters their phone number on the exchange and gets an SMS with a code. The code is valid for 6 minutes.
• Action codes. Users who chose SMS for their verification codes get them by text, for example when they withdraw or reset their password.
• Deposit and withdrawal messages, such as "Your USDT deposit for amount 15.9987 is confirmed".

The message text is fixed. You can't change it from the settings. If you need your own wording, use the AWS SNS plugin.

How it works

• The plugin checks for another SMS plugin when it starts. If one is already installed, it doesn't start and emails your exchange's audit address that the second SMS plugin was blocked.
• If the service plan ID, API token or sender is missing, the plugin doesn't start and nothing is sent.
• A user who requests too many codes, or enters too many wrong ones, is blocked from SMS verification for 24 hours. They see "Too many requests. Your account is blocked for 24 hours".

Compare the SMS plugins

All four SMS plugins send the same three kinds of message, and each one can be turned off in the settings:

• Deposit SMS (send_sms_deposit): sent when a deposit completes.
• Withdrawal SMS (send_sms_withdrawal): sent when a withdrawal completes.
• Verification SMS (send_sms_user_verification): codes for sensitive actions, such as withdrawals and password resets, for users who chose SMS for their codes. Phone number verification codes are always sent.

They differ in the provider and in a few details:

Plugin	Provider account you need	Edit the message text	Phone number treated as a login credential
SMS via AWS SNS (sms)	AWS, with SNS	Yes	Yes
Telnyx (telnyx)	Telnyx, with a messaging-enabled number	No	Yes
Messente (messente-sms)	Messente, with API access	No	Yes
Sinch (sinch)	Sinch, with an SMS service plan	No	No

You can install only one SMS plugin at a time. To switch, remove the one you have, then install the new one.

Troubleshooting

• No SMS arrives. Check the service plan ID and API token, and that region matches the region of your service plan. Check that the sender is allowed in the user's country. Check that no other SMS plugin is installed. Then check the plugin logs.
• "Invalid phone number". The number the user entered isn't a valid phone number. Ask them to enter it with the country code.

Need help? Open a ticket from your HollaEx dashboard.