As a free service to our customers and to prevent them from unnecessary cost, we check all phone numbers used on SMS.to to see whether they are valid or not. An invalid format can mean:
- It does not exist at all or
- It was provided in an invalid format
so sending towards this these numbers would fail anyhow but would result in a charge for both SMS.to and for our customers.
To check number validity, we recommend this 3rd party tool: https://libphonenumber.appspot.com/
We will only completely prevent sending (via sms.to) in case a campaign is configured to go too 100% invalid numbers.
If only a part of all numbers of a campaign are invalid, we allow sending to avoid interruptions by forcing our users to clean their list of numbers before being able to send.