--- title: "What is bulk SMS and how does it work?" description: "Bulk SMS lets you deliver one message to thousands of recipients in a single request. This guide covers how it works, pricing mechanics, Turkey-specific regulation, and how iletiMerkezi implements it." slug: /en/docs/guides/toplu-sms-nedir locale: en audience: general last_updated: 2026-04-30 target_queries: [what is bulk sms, bulk sms turkey, bulk sms api, sms marketing turkey, transactional sms] related: [iys-rehberi, sms-basligi-nasil-alinir, kvkk-sms] alternates: tr: https://www.iletimerkezi.com/docs/guides/toplu-sms-nedir en: https://www.iletimerkezi.com/en/docs/guides/toplu-sms-nedir --- # 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. ## Summary - 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 that exceed the single-part limit (150 characters in Turkish-character mode, for example) 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](../api/send-sms.md), [get-report](../api/get-report.md), [webhooks](../api/webhooks.md). ## Character limits and message parts In the Turkey-typical B186 carrier-header format, the per-part character limit depends on the encoding mode. First part / subsequent parts: | Character mode | First part | Subsequent parts | |---|---|---| | English / GSM-7 (ASCII only) | 155 | 153 | | Turkish-character mode (`ş, ğ, ı, ç, ö, ü, İ, Ş, Ğ, Ç, Ö, Ü`) | 150 | 148 | | Unicode / UCS-2 (emoji or non-Latin scripts, e.g. Chinese, Russian, Arabic) | 65 | 63 | - Turkish-character mode is **distinct from UCS-2**: it uses a 7-bit Turkish alphabet with a 150/148 limit. If a message contains an emoji or any non-Latin character, it falls back to UCS-2 and the limit drops to 65/63. - Multi-part messages are billed per part by the carrier; up to **7 parts / ~1071 chars** are supported. - The character mode is configured at the account level from the panel. The default mode is **English (GSM-7)**; to send Turkish characters or Unicode you must first enable Universal Language Support at [`panel.iletimerkezi.com/settings/sms/encoding`](https://panel.iletimerkezi.com/settings/sms/encoding). See [API overview](../api/overview.md) for details. 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](./iys-rehberi). - **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](./kvkk-sms). - **Sender ID:** Sending under a brand name requires a BTK-approved sender ID. Process: [How to get an SMS sender ID](./sms-basligi-nasil-alinir). ## 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](https://www.iletimerkezi.com/yurtdisi-sms-fiyatlari/US). ## 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](../api/cancel-order.md). **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](../api/send-sms.md) and receive real-time delivery reports via [webhooks](../api/webhooks.md). - **MCP server:** Send SMS directly from MCP-aware LLM clients like Claude Desktop, Cursor, and Cline. See: [MCP server guide](../mcp). [Sign up](https://panel.iletimerkezi.com/auth/signup), [API overview](../api/overview.md), [Pricing](https://www.iletimerkezi.com/yurtdisi-sms-fiyatlari/US) ## Related - [İYS guide](./iys-rehberi) - [How to get an SMS sender ID](./sms-basligi-nasil-alinir) - [KVKK and SMS](./kvkk-sms) - [send-sms API](../api/send-sms.md) - [API overview](../api/overview.md)