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What is bulk SMS and how does it work?

Bulk SMS is a messaging method that delivers the same (or personalised) short message to hundreds or thousands of recipients with a single send instruction. Businesses use it for campaigns, reminders, OTP verification, order updates, and operational alerts; technically it is triggered through an SMS API or panel as a single request, with an approved sender ID on the sender side and a valid consent record on the recipient side.

TL;DR

  • Bulk SMS = one request, many recipients. Used for campaigns, OTP, notifications, operational alerts.
  • In Turkey, commercial bulk SMS requires İYS consent; informational messages (orders, appointments, OTP) fall outside İYS.
  • Sender ID (header) requires BTK approval; iletiMerkezi provides the APITEST sender so you can test before approval.
  • Pricing is credit-based; messages over 155 characters are billed as multiple SMS parts. Undelivered messages are free at iletiMerkezi.
  • Sending happens through the panel, the API, or the MCP server — all use the same backend.

Common use cases

  • Campaign / promotion: Product launch, discount, marketing offer. Commercial content — İYS consent is mandatory.
  • Operational notification: Order confirmation, shipping status, appointment reminder, payment receipt. Outside İYS, informational.
  • OTP / verification: One-time passwords, login confirmation, transaction approval. Outside İYS; low latency and high deliverability are critical.
  • Critical alert: Service outage, fault, security warning.
  • Call-centre follow-up: Summary or next-step SMS after a customer call.

All of these can be triggered with a single SMS API call: sender ID, recipient list, message body, and optional scheduling.

How bulk SMS works under the hood

  1. Send request: The customer creates a send request via the panel or API (recipient list + message + sender ID).
  2. Validation: The provider (e.g. iletiMerkezi) checks the sender ID is approved, the recipients are not blacklisted, and the account has the required permissions.
  3. İYS check (commercial content): The platform verifies the recipient has consent on file at İYS; non-consented numbers are dropped.
  4. Hand-off to the carrier: The message is dispatched to the recipient's mobile network operator (Turkcell / Vodafone / Türk Telekom in Turkey).
  5. Delivery report: The carrier returns a DLR (Delivery Receipt) indicating whether the message reached the device. The provider exposes that report through API + webhook.

At iletiMerkezi, delivery reports are available via the get-report endpoint or pushed via webhook. See: send-sms, get-report, webhooks.

Character limits and message parts

  • SMS containing Turkish characters (ı, ğ, ş, ç, ö, ü) is encoded as Unicode (UCS-2); single SMS = max 70 chars.
  • ASCII-only SMS uses GSM-7 encoding; single SMS = max 160 chars.
  • iletiMerkezi panel and API enforce the Turkey-typical B186 carrier header format: first part 155 / subsequent parts 153 chars (Turkish content) or 160 / 153 (ASCII).
  • Multi-part messages are billed per part by the carrier; up to 7 parts / ~1071 chars are supported.

Practical rule: keep campaign copy short, and use a short-link service such as iim.to to reduce message length.

Turkey regulation: İYS, KVKK, BTK

  • BTK licence: To operate as a bulk SMS provider in Turkey, an STH (Limited Telecommunications Service) authorisation is required from BTK (Information and Communication Technologies Authority). iletiMerkezi is BTK-licensed.
  • İYS (Commercial Messaging Consent Registry): For commercial content, recipient consent must be on file at İYS. Informational SMS (order, appointment, OTP) is exempt. See: İYS guide.
  • KVKK: A phone number is personal data. KVKK compliance requires explicit consent, a clarification text, and a retention policy; İYS consent does not replace KVKK — these are separate obligations. See: KVKK and SMS.
  • Sender ID: Sending under a brand name requires a BTK-approved sender ID. Process: How to get an SMS sender ID.

Pricing model

Bulk SMS pricing in Turkey is credit-based: 1 credit = 1 SMS part. Higher volume reduces the per-credit price. iletiMerkezi specifics:

  • New accounts get 100 free SMS welcome credits automatically.
  • Undelivered SMS is free; only delivered messages are deducted. (get-report returns delivered count + price, which is the source of truth.)
  • International sending is billed in TRY balance, not credits; price varies by destination country and carrier.
  • Test sends with the APITEST sender ID are not billed.

Current price tiers: iletiMerkezi pricing page.

Frequently asked questions

Q: How long does the approval process take? Account creation completes in minutes. Sender ID approval at BTK typically takes 1–2 business days; during that window you can run technical tests with APITEST, but real recipient sends require an approved brand sender ID.

Q: How many recipients can I send to in one API call? The iletiMerkezi send-sms endpoint accepts 100,000+ recipients per request. Distribution to carriers is handled by iletiMerkezi; the backend returns a single orderId, which you use to query reports.

Q: Can I cancel an SMS after sending it? Only future-scheduled orders that have not started dispatch can be cancelled. Once a message has been handed off to the carrier, it cannot be recalled. See: cancel-order.

Q: Is bulk SMS legal? Yes. Sending to İYS-consented recipients with a BTK-approved sender ID is fully compliant in Turkey. Sending without consent is subject to administrative fines under KVKK and Law No. 6563 on Electronic Commerce.

Q: What happens if the recipient's phone is off? The carrier holds the message for up to 24–72 hours; if the device comes online it is delivered, otherwise it falls into "undelivered" state and is not billed by iletiMerkezi.

How to do it on iletiMerkezi

Three options:

  • Panel: Sign up, request a sender ID, add recipients via Excel or manually, write the message, send. No technical skills required.
  • API: Integrate into your own software. Send with send-sms and receive real-time delivery reports via webhooks.
  • MCP server: Send SMS directly from MCP-aware LLM clients like Claude Desktop, Cursor, and Cline. See: MCP server guide.

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Last updated: 2026-04-30 · Türkçe