UK SMS: International Long Codes Blocked
Stay compliant1 min readUpdated 2026-03-12
UK SMS: International Long Codes Blocked
UK mobile carriers increasingly block SMS sent from international long codes (e.g., US +1 numbers sending to UK +44 numbers). This is a carrier-level filter to prevent spam and grey-route messaging.
What's Blocked
- SMS from US local numbers (+1) to UK mobile numbers (+44).
- SMS from other international long codes to UK numbers.
- This affects both manual and automated messages.
What Works
| Sending Method | Delivery to UK |
|---|---|
| UK local number (+44) | Delivered |
| Alphanumeric Sender ID | Delivered (one-way, no replies) |
| US local number (+1) | Likely blocked |
| US toll-free (+1 800) | May be blocked |
Recommendation
If you regularly message UK recipients:
- Purchase a UK local number through JustCall (Settings → Phone Numbers → Add Number → select United Kingdom).
- Or enable an Alphanumeric Sender ID for one-way messaging (see Alphanumeric Sender ID Overview).
Related Articles
Was this helpful?