SMS

SMS is the universal fallback: it reaches every handset, needs no app, and is the right channel for one-time passcodes and time-critical alerts.

Sender identity

Registration rules are set per country. Alphanumeric sender IDs are supported in much of Europe, pre-registered in some markets, and blocked in others — where blocked, traffic sends from a long number.

Opt-out handling

Inbound STOP-style keywords are detected and written to the contact's consent record automatically. Once opted out, the contact is excluded from marketing sends on the channel. Keep transactional and marketing consent separate.

Cost and length

Messages are billed per segment. A GSM-7 segment is 160 characters; adding a single emoji or non-GSM character switches the message to UCS-2 and drops the segment to 70 characters. Check the segment count before a bulk send.

Fallback

SMS is commonly configured as the automatic fallback when a WhatsApp or RCS message cannot be delivered.