Carrier and provider requirements

Carriers and messaging platforms enforce their own policies beyond the law — and violating them can block your traffic.

Updated 2 min readMaintained by Landing Zone

Legal rules are only one layer of messaging compliance. Carriers and messaging platforms enforce a second, private layer of policy on the traffic they carry — and they enforce it technically, by filtering, blocking, and suspending. A message can satisfy every legal requirement and still never reach a phone.

What carriers and platforms require

  • Registration. Business SMS on local numbers requires A2P 10DLC registration. In Landing Zone, the Trust Center tracks your registration status, and SMS sending gates on approved status — see the A2P 10DLC setup guide.
  • Content rules. Carriers restrict or prohibit certain content categories — commonly summarized as SHAFT (sex, hate, alcohol, firearms, tobacco) — along with deceptive or misleading content, regardless of legality.
  • Volume limits. Throughput and daily volume allowances are typically tied to your registration, and traffic beyond them can be queued or dropped.
  • Filtering. Carriers score traffic continuously using complaints, content patterns, and sending behavior, and filter messages that look like spam — sometimes without telling anyone.

The consequences are practical

Violating carrier or platform policy risks filtered or blocked messages, suspension of your sending numbers, and suspension of the account behind them — even when the message itself is otherwise lawful. Legal compliance is necessary for messaging, but it is not sufficient for delivery.

Policies can change without notice

Carrier and provider policies may apply and change without notice. Content that delivered cleanly last quarter can be filtered today, and registration or volume expectations can tighten. Treat carrier policy as a moving target you monitor, not a box you check once.

What Landing Zone does and does not do

Landing Zone tracks A2P registration status in the Trust Center and holds SMS sending until registration is approved. It also appends "Reply STOP to opt out." to the first outbound SMS to a contact, and its suppression, quiet-hour, and cooldown controls reduce the complaint-generating behavior that draws filtering.

It cannot guarantee delivery, override carrier filtering, or judge whether your content fits every carrier's policy.

Your responsibilities

Complete and maintain your registrations before scaling, keep your content within carrier policy, and watch your delivery metrics for early signs of filtering — see SMS delivery issues and the broader SMS channel page.