Our API plans offer everything you’ll need in an SMS gateway service. GREXT™ is a simple, pay-as-you-go, web-based message app. Simple SMS for small apps and calendaring alerts. Works on all carriers and reaches where shortcodes cannot. Connect to a Short Code reaching the U.S., Canada or international. Add Ons The SMS Authentication PIN is popular for security validation. Text from your current business landline. Send media-rich content with MMS. Text from your current toll-free number.