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

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

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. See API overview 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.
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.

Last updated: 2026-04-30 · Türkçe