Historically, mobile carriers operated email-to-SMS gateways that converted a standard SMTP message sent to 10digitnumber@carrier-gateway.example into an SMS text message. While some legacy gateways still exist, relying on email-to-SMS for production notifications or marketing is increasingly unreliable.
How email-to-SMS gateways work
When an MTA sends an email to a carrier gateway domain (for example, legacy domains such as vtext.com or txt.att.net), the carrier's gateway server accepts the message over SMTP, strips HTML formatting, truncates the body to SMS character limits and routes it over the cellular network.
Operational and deliverability limitations
- Gateway deprecations and silent filtering: several major carriers have retired or severely rate-limited consumer email-to-SMS gateways to combat spam and phishing (smishing). Messages often fail silently without returning a standard RFC 3463 bounce code.
- Sender authentication requirements: gateways that still operate enforce strict SPF, DKIM and DMARC alignment on the sending domain.
- List hygiene impact: gateway addresses (
5551234567@carrier.example) should never be mixed into standard email marketing lists. When cleaning lists with ValidReach, separate phone-gateway addresses from real user mailboxes and move SMS alerts to a dedicated SMS API with explicit opt-in.
Sources
- IETF RFC 5321 — Simple Mail Transfer Protocol — accessed 2026-11-04
- IETF RFC 3463 — Enhanced Mail System Status Codes — accessed 2026-11-04
- ValidReach Email Verifier — accessed 2026-11-04
