From SMS Wiki
EnterpriseSMS API offers three different types of SMTP interfaces for sending SMS messages to any network. With all of them the process is as follows:
- Your application sends email with relevant authentication and messaging parameters
- Our service authenticates this requests, creates SMS message and sends it
- Your account is billed for this transaction
The difference in these three methods is in the authentication used.
- SMTP server authentication - your application connects to our SMTP service and sends email with the request
- WebText (or PIN) authentication - in some cases, you do not have the ability to connect to our SMTP server. PIN authentication provides a less secure alternative. You send email using any SMTP server and in the subject of this message you specify PIN code.
- IP address authentication - We can record the IP address of your mail server and use this for authentication.