--- title: "Business messaging glossary" description: "Clear definitions of SMS, WhatsApp, RCS, voice, API and compliance terms, with GCC and MENA specifics. Written by BroadNet's messaging specialists." canonical: "https://omnichannels.ai/glossary/" language: "en" updated: "2026-10-11" publisher: "BroadNet Technologies" brand: "OmniChannels.ai" --- # Business messaging glossary Canonical: https://omnichannels.ai/glossary/ Language: en Publisher: OmniChannels.ai by BroadNet Technologies Clear definitions of SMS, WhatsApp, RCS, voice, API and compliance terms, with GCC and MENA specifics. Written by BroadNet's messaging specialists. ## SMS and telecom - [A2P SMS](https://omnichannels.ai/glossary/a2p-sms/): A2P SMS (application-to-person SMS) is a text message sent by a software application to a mobile user, such as an OTP, delivery alert or marketing offer, rather than by one person to another. - [Alphanumeric sender ID](https://omnichannels.ai/glossary/alphanumeric-sender-id/): An alphanumeric sender ID is a text sender name such as “AcmeBank” shown instead of a phone number on an SMS. It can contain up to 11 characters and cannot receive replies. - [Bulk SMS](https://omnichannels.ai/glossary/bulk-sms/): Bulk SMS is the sending of the same or personalised text message to a large list of recipients in one operation, typically for marketing campaigns, announcements or alerts. - [Concatenated SMS (UDH)](https://omnichannels.ai/glossary/concatenated-sms/): Concatenated SMS is a long message sent as several linked segments. A User Data Header (UDH) in each segment carries a reference number, the total parts and the part number so the phone can reassemble them. - [Delivery receipt (DLR)](https://omnichannels.ai/glossary/delivery-receipt/): A delivery receipt (DLR) is a status message returned by the operator network that tells the sender whether an SMS was delivered to the handset, expired, or failed, along with timestamps and an error code. - [Direct operator route](https://omnichannels.ai/glossary/direct-route/): A direct operator route is an SMS connection where the provider has its own agreement and technical link with the destination mobile operator, rather than handing traffic to other intermediaries. - [E.164 number format](https://omnichannels.ai/glossary/e164/): E.164 is the ITU-T international numbering plan. An E.164 number is written with a leading + followed by the country code and national number, up to 15 digits in total, with no spaces or punctuation. - [Flash SMS](https://omnichannels.ai/glossary/flash-sms/): A flash SMS is a Class 0 text message that the phone displays immediately on screen without storing it in the inbox by default. It is defined by the message class in the data coding scheme. - [Grey route](https://omnichannels.ai/glossary/grey-route/): A grey route delivers A2P SMS to an operator without the operator’s commercial agreement, for example through SIM banks or P2P interconnects, avoiding the A2P termination charge. - [GSM-7 encoding](https://omnichannels.ai/glossary/gsm-7/): GSM-7 is the default 7-bit SMS alphabet defined in 3GPP TS 23.038 (formerly GSM 03.38). It fits 160 characters in a single SMS, or 153 per segment when a message is split. - [HLR lookup](https://omnichannels.ai/glossary/hlr-lookup/): An HLR lookup queries the mobile network’s subscriber database to check whether a number is valid and active, which operator currently serves it (after porting) and sometimes whether it is roaming. - [Long code (virtual number)](https://omnichannels.ai/glossary/long-code/): A long code is a standard-length phone number, often a virtual mobile number hosted by a provider, used by a business to send and receive SMS. Unlike a short code it is usually reachable internationally. - [MCC/MNC](https://omnichannels.ai/glossary/mcc-mnc/): MCC/MNC is the pair of codes that identifies a mobile network: the Mobile Country Code (3 digits) identifies the country, and the Mobile Network Code (2 or 3 digits) identifies the operator within it. - [Mobile number portability](https://omnichannels.ai/glossary/mnp/): Mobile number portability (MNP) lets subscribers keep their phone number when switching mobile operators. As a result, a number’s prefix no longer reliably shows which operator serves it. - [OTT messaging](https://omnichannels.ai/glossary/ott-messaging/): OTT (over-the-top) messaging is chat delivered over an internet connection by an app such as WhatsApp, Telegram or Messenger, rather than through the mobile operator’s SMS service. - [P2P messaging](https://omnichannels.ai/glossary/p2p-sms/): P2P messaging (person-to-person) is SMS sent between two individual subscribers from their own phones, as opposed to A2P traffic generated by business applications. - [Promotional SMS](https://omnichannels.ai/glossary/promotional-sms/): Promotional SMS is any text message whose purpose is to market products, services or offers. It is usually subject to opt-in consent, opt-out handling, sending-hour limits and sender ID rules. - [Sender ID](https://omnichannels.ai/glossary/sender-id/): A sender ID is the value shown as the sender of an SMS on the recipient’s phone: a brand name (alphanumeric), a short code or a full phone number (long code). - [Short code](https://omnichannels.ai/glossary/short-code/): A short code is a short phone number, usually 3–8 digits, that businesses use to send and receive SMS at volume, for example for opt-ins, voting, OTPs and two-way campaigns. - [SMPP](https://omnichannels.ai/glossary/smpp/): SMPP (Short Message Peer-to-Peer) is an open binary protocol over TCP that applications (ESMEs) and SMS providers use to exchange SMS with an SMSC. Version 3.4 is the most widely deployed. - [SMPP bind](https://omnichannels.ai/glossary/smpp-bind/): An SMPP bind is the login operation that opens an SMPP session. The client authenticates with a system_id and password and chooses to bind as transmitter (send), receiver (receive) or transceiver (both). - [SMS aggregator](https://omnichannels.ai/glossary/sms-aggregator/): An SMS aggregator is a company that connects businesses and other providers to many mobile operators, combining traffic from many senders and routing it to operator networks through direct or partner connections. - [SMS firewall](https://omnichannels.ai/glossary/sms-firewall/): An SMS firewall is an operator-side system that inspects incoming SMS traffic and blocks or charges messages that arrive over unauthorised routes, carry spam or fraud, or break the operator’s A2P rules. - [SMS gateway](https://omnichannels.ai/glossary/sms-gateway/): An SMS gateway is a system that converts messages between applications (over HTTP, SMPP or email) and mobile networks, handling routing, encoding, segmentation and delivery receipts. - [SMS segment](https://omnichannels.ai/glossary/sms-segment/): An SMS segment is one 140-octet transport unit of a text message. A message longer than one segment is split into several, and each segment is usually billed as a separate SMS. - [SMSC](https://omnichannels.ai/glossary/smsc/): An SMSC (Short Message Service Centre) is the network element that stores, forwards and delivers SMS. It accepts messages from phones or applications and attempts delivery to the recipient’s handset, retrying until the message expires. - [submit_sm](https://omnichannels.ai/glossary/submit-sm/): submit_sm is the SMPP v3.4 operation (command_id 0x00000004) an application uses to submit a single SMS to the SMSC. The SMSC replies with submit_sm_resp containing a message_id used to match later delivery receipts. - [Throughput (TPS)](https://omnichannels.ai/glossary/throughput-tps/): Throughput, measured in TPS (transactions or messages per second), is the rate at which a provider accepts messages on an account, bind or route. Sending faster than the agreed TPS causes throttling or rejection. - [Transactional SMS](https://omnichannels.ai/glossary/transactional-sms/): Transactional SMS is a non-marketing message triggered by a customer’s action or account event, such as an OTP, order confirmation, delivery update or payment alert. - [Two-way SMS](https://omnichannels.ai/glossary/two-way-sms/): Two-way SMS lets a business both send messages (mobile-terminated, MT) and receive replies (mobile-originated, MO) from customers, using a short code or long code that can accept inbound texts. - [UCS-2 encoding](https://omnichannels.ai/glossary/ucs-2/): UCS-2 is the 16-bit character encoding SMS uses for text outside the GSM-7 alphabet, such as Arabic, Chinese or emoji. One SMS holds 70 UCS-2 characters, or 67 per segment in a multipart message. - [Unicode SMS](https://omnichannels.ai/glossary/unicode-sms/): Unicode SMS is a text message sent with UCS-2 encoding so it can contain characters outside the GSM-7 alphabet, such as Arabic script or emoji. It holds 70 characters per single SMS and 67 per segment. - [Wholesale A2P SMS](https://omnichannels.ai/glossary/wholesale-sms/): Wholesale A2P SMS is high-volume business messaging traffic traded between providers, aggregators and operators at carrier rates, usually over SMPP connections, as opposed to retail SMS sold to individual businesses through a portal or API. ## GCC and MENA - [AD prefix (UAE promotional SMS)](https://omnichannels.ai/glossary/ad-prefix/): In the UAE, the AD prefix is a mandatory "AD-" at the start of the sender ID of every promotional SMS, for example AD-ACME. It marks the message as advertising; transactional senders for OTPs and alerts do not use it. - [CITRA (Kuwait)](https://omnichannels.ai/glossary/citra/): CITRA (Communication and Information Technology Regulatory Authority) is Kuwait's regulator for telecoms and IT. Business messaging in Kuwait follows its framework, with sender IDs registered through the mobile operators. - [CRA (Qatar)](https://omnichannels.ai/glossary/cra-qatar/): The CRA (Communications Regulatory Authority) is Qatar's telecoms regulator. Its Spam Regulation and consumer-protection framework govern commercial SMS, including consent, opt-out wording and the hours when direct-marketing messages may be sent. - [CST (Saudi Arabia)](https://omnichannels.ai/glossary/cst/): The CST (Communications, Space and Technology Commission) is Saudi Arabia's telecoms regulator, formerly called CITC. It governs A2P messaging in the Kingdom, including sender ID approval and its Regulations for Curbing SPAM Messages and Calls. - [NTRA (Egypt)](https://omnichannels.ai/glossary/ntra/): The NTRA (National Telecom Regulatory Authority) is Egypt's telecoms regulator. Business sender IDs in Egypt need NTRA and operator approval, and marketing consent falls under Egypt's Personal Data Protection Law No. 151 of 2020. - [TDRA (UAE)](https://omnichannels.ai/glossary/tdra/): The TDRA (Telecommunications and Digital Government Regulatory Authority) is the UAE's telecoms regulator. It sets the rules for business messaging and telemarketing, including sender ID registration, the AD prefix on promotional SMS, opt-out handling and quiet hours. ## Platform - [AI agent](https://omnichannels.ai/glossary/ai-agent/): An AI agent is software built on a language model that pursues a goal by planning steps, calling tools and business systems (such as a CRM, booking engine or messaging API) and using the results, rather than only generating a reply. - [Channel fallback](https://omnichannels.ai/glossary/channel-fallback/): Channel fallback automatically resends a message over a second channel when the first one cannot deliver it, for example trying WhatsApp, then RCS, then SMS, based on rules such as "recipient not on the channel" or "not delivered within 60 seconds". - [Chatbot](https://omnichannels.ai/glossary/chatbot/): A chatbot is software that converses with users in a messaging channel or web chat, answering questions and guiding them through tasks with buttons, menus or free text, and passing the conversation to a human when it cannot help. - [Click-through rate (messaging)](https://omnichannels.ai/glossary/ctr/): In messaging, click-through rate (CTR) is the share of delivered messages whose link or button was clicked, calculated as unique clicks divided by delivered messages. It measures how well a message prompts action. - [Conversational AI](https://omnichannels.ai/glossary/conversational-ai/): Conversational AI is the set of technologies, such as natural language understanding, large language models, speech recognition and text-to-speech, that let software hold natural conversations with people in text or voice and complete tasks for them. - [Conversion attribution (UTM)](https://omnichannels.ai/glossary/conversion-attribution/): Conversion attribution links a sale, sign-up or other goal back to the message that caused it. In messaging this is usually done with UTM parameters added to links, so analytics tools can credit the right channel, campaign and message. - [CPaaS](https://omnichannels.ai/glossary/cpaas/): CPaaS (Communications Platform as a Service) is a cloud platform that lets businesses add messaging, voice and verification to their own apps through APIs, instead of building telecom infrastructure. - [Delivery rate](https://omnichannels.ai/glossary/delivery-rate/): Delivery rate is the share of sent messages that the network or channel confirms as delivered to the recipient's device, usually calculated as delivered messages divided by messages submitted, for a given campaign, route, country or period. - [Human handover](https://omnichannels.ai/glossary/human-handover/): Human handover is the transfer of a conversation from a chatbot or AI agent to a human agent, together with the conversation history and collected details, so the customer does not have to repeat themselves. - [Instagram messaging API](https://omnichannels.ai/glossary/instagram-messaging-api/): The Instagram messaging API lets a business read and reply to Instagram Direct messages on its Instagram professional account from its own software, such as a shared inbox or chatbot, within Meta's messaging windows. - [Messenger Platform](https://omnichannels.ai/glossary/messenger-platform/): The Messenger Platform is Meta's set of APIs and webhooks that lets businesses send and receive messages with people through their Facebook Page on Messenger, and through Instagram professional accounts, from their own software. - [Omnichannel inbox](https://omnichannels.ai/glossary/omnichannel-inbox/): An omnichannel inbox brings customer conversations from WhatsApp, SMS, RCS, Instagram, Messenger, Telegram, email and other channels into one workspace, with one thread per customer, so agents can reply, assign and track conversations without switching tools. - [Push notification](https://omnichannels.ai/glossary/push-notification/): A push notification is a message sent from a server to a user's device through the operating system's push service, such as Firebase Cloud Messaging or the Apple Push Notification service. It appears even when the app or website is not open. - [Read rate](https://omnichannels.ai/glossary/read-rate/): Read rate is the share of delivered messages that the recipient opened, based on read receipts reported by channels such as WhatsApp and RCS. Standard SMS has no read receipts, so read rate cannot be measured for it. - [SMS reseller](https://omnichannels.ai/glossary/sms-reseller/): An SMS reseller buys A2P messaging capacity from a provider at wholesale or discounted rates and sells it to its own customers at retail prices, usually through a branded portal and sub-accounts, earning the margin between the two. - [Sub-account](https://omnichannels.ai/glossary/sub-account/): A sub-account is a separate account created under a parent (reseller or enterprise) account on a messaging platform, with its own users, credit, sender IDs, pricing and settings, so each client, brand or department is isolated and billed independently. - [Telegram bot](https://omnichannels.ai/glossary/telegram-bot/): A Telegram bot is an automated Telegram account, controlled through Telegram's HTTP-based Bot API, that businesses use to send notifications, answer questions and run conversational services for users who have started a chat with it. - [UCaaS vs CPaaS](https://omnichannels.ai/glossary/ucaas-vs-cpaas/): UCaaS is a ready-made cloud phone, meeting and team-chat service for employees; CPaaS is a set of APIs developers use to build communications into their own apps and customer journeys. - [White-label messaging](https://omnichannels.ai/glossary/white-label-messaging/): White-label messaging is a messaging platform that a reseller, agency or telecom operator sells under its own brand: the console, reports, invoices and domain carry the reseller's name and logo, while the provider runs the underlying channels and infrastructure. ## Voice - [AI voice agent](https://omnichannels.ai/glossary/ai-voice-agent/): An AI voice agent is software that holds a spoken phone conversation: it transcribes the caller's speech, uses a language model to understand and decide what to do, speaks a reply with text-to-speech, and can act in business systems or hand over to a human. - [Answering machine detection](https://omnichannels.ai/glossary/answering-machine-detection/): Answering machine detection (AMD) analyses the first seconds of an answered outbound call to decide whether a person or a voicemail system picked up, so the dialer can connect a live agent, start an automated flow or leave a pre-recorded voicemail. - [Bring your own carrier (BYOC)](https://omnichannels.ai/glossary/byoc/): Bring your own carrier (BYOC) lets a business connect its existing telecom carrier contracts and phone numbers to a cloud voice or contact-centre platform over SIP trunks, instead of buying minutes and numbers from the platform provider. - [Flash call verification](https://omnichannels.ai/glossary/flash-call/): Flash call verification confirms a phone number by placing a very short call that is dropped before it is answered; the last digits of the calling number act as the one-time code, which the app reads automatically or the user enters. - [IVR](https://omnichannels.ai/glossary/ivr/): IVR (interactive voice response) is a phone system that answers or places calls automatically, plays recorded or text-to-speech prompts, and lets callers choose options by pressing keypad digits (DTMF) or speaking, before routing them or completing a task. - [SIP trunk](https://omnichannels.ai/glossary/sip-trunk/): A SIP trunk is a virtual connection that carries phone calls over IP between a business phone system or voice platform and a carrier, using the Session Initiation Protocol (SIP) for call setup and RTP for the audio. - [Text-to-speech (TTS)](https://omnichannels.ai/glossary/text-to-speech/): Text-to-speech (TTS) converts written text into spoken audio. In business voice systems it lets IVR prompts, voice OTPs, reminders and AI voice agents speak dynamic content without pre-recording every sentence. - [Voice OTP](https://omnichannels.ai/glossary/voice-otp/): A voice OTP is a one-time password delivered by an automated phone call: a text-to-speech engine reads the code aloud, usually twice, so the user can type it into an app or website to verify their phone number or log in. ## Fraud and security - [Artificial inflation of traffic](https://omnichannels.ai/glossary/artificial-inflation-of-traffic/): Artificial inflation of traffic (AIT) is a type of A2P SMS fraud in which fake traffic is generated through a business's apps or websites so that parties in the delivery chain profit from the termination revenue, while the business pays for messages with no real recipient. - [International revenue share fraud](https://omnichannels.ai/glossary/irsf/): International revenue share fraud (IRSF) generates calls or messages to high-cost international number ranges controlled by the fraudster, who receives part of the termination revenue, while the business or subscriber that originated the traffic pays the bill. - [SIM box fraud](https://omnichannels.ai/glossary/sim-box-fraud/): SIM box fraud diverts international calls or A2P SMS away from official interconnect routes by terminating them through banks of local SIM cards, so the traffic looks like cheap local person-to-person traffic and the operator loses its international termination revenue. - [SMS pumping (AIT)](https://omnichannels.ai/glossary/sms-pumping/): SMS pumping is fraud in which bots trigger large numbers of SMS messages, usually OTPs, from a business's sign-up or login form to numbers controlled by the fraudster, who takes a share of the termination revenue while the business pays for messages nobody uses. ## WhatsApp - [Authentication template](https://omnichannels.ai/glossary/authentication-template/): An authentication template is the WhatsApp template category reserved for one-time passwords and verification codes. It uses fixed preset text plus a one-tap autofill, copy-code or zero-tap option, and Meta does not allow URLs, media or emojis in it. - [Business Solution Provider (BSP)](https://omnichannels.ai/glossary/bsp/): A Business Solution Provider (BSP) is a company authorised by Meta to give other businesses access to the WhatsApp Business Platform, typically handling onboarding, billing, integration and support. Meta's current term for a BSP is Solution Partner. - [Click-to-WhatsApp ads](https://omnichannels.ai/glossary/click-to-whatsapp-ads/): Click-to-WhatsApp ads are Facebook and Instagram ads whose button opens a WhatsApp chat with the business. If the business replies within 24 hours to a user who messages through one on the mobile app, a free entry point window opens that may remain open for up to 7 days, during which Meta does not charge for the business's marketing, utility, authentication or service messages. - [Customer service window](https://omnichannels.ai/glossary/customer-service-window/): The customer service window is the 24-hour period that starts when a WhatsApp user messages or calls a business. While it is open the business can send free-form (non-template) messages. Once it closes, only approved templates can be sent. - [Embedded Signup](https://omnichannels.ai/glossary/embedded-signup/): Embedded Signup is Meta's onboarding flow that a partner embeds in its website so a business can create or select its business portfolio and WhatsApp Business Account, verify a phone number and grant the partner access, all in one guided window. - [Interactive messages](https://omnichannels.ai/glossary/interactive-messages/): Interactive messages are WhatsApp message types with tappable elements, such as reply buttons, list menus, call-to-action URL buttons, location requests and product messages, that a business can send inside a customer service window. - [Marketing template](https://omnichannels.ai/glossary/marketing-template/): A marketing template is a WhatsApp message template used for promotions, offers, announcements, re-engagement or any content that is not strictly transactional or an OTP. It is the most flexible category and is charged per delivered message. - [Message template](https://omnichannels.ai/glossary/message-template/): A message template is a pre-approved WhatsApp message format, with fixed text, optional variables, media and buttons, that a business must use to message a customer outside the 24-hour customer service window. Each template is categorised as marketing, utility or authentication. - [Official business account (green tick)](https://omnichannels.ai/glossary/green-tick/): An Official Business Account (OBA) is a WhatsApp business phone number that Meta has verified as belonging to an authentic, notable business. It shows a checkmark next to the business name. The badge was historically green and Meta's documentation now describes it as blue. - [Quality rating](https://omnichannels.ai/glossary/quality-rating/): A quality rating is Meta's assessment of how WhatsApp users respond to a business's messages, based on usage, feedback such as blocks and reports, and engagement such as read rates. Meta rates both templates and phone numbers. - [Template category](https://omnichannels.ai/glossary/template-category/): A template category is the label (marketing, utility or authentication) that Meta assigns to every WhatsApp message template. It determines what content is allowed and how much each delivered message costs. - [Utility template](https://omnichannels.ai/glossary/utility-template/): A utility template is a non-promotional WhatsApp message template that follows up on a specific user action or request, such as an order confirmation, shipping update, appointment reminder or account alert. - [wa.me link](https://omnichannels.ai/glossary/wa-me-link/): A wa.me link is a WhatsApp click-to-chat URL that opens a chat with a specific phone number, optionally with prefilled text, without the user saving the number. The format is https://wa.me/?text=. - [WhatsApp Business Account (WABA)](https://omnichannels.ai/glossary/waba/): A WhatsApp Business Account (WABA) is the Meta asset that represents a business on the WhatsApp Business Platform. It holds the business phone numbers and message templates, and every API message is sent through a WABA. - [WhatsApp Business API](https://omnichannels.ai/glossary/whatsapp-business-api/): The WhatsApp Business API is Meta's programmatic interface that lets medium and large businesses send and receive WhatsApp messages from their own software, at scale, through a verified business phone number. Today it is delivered as Meta's Cloud API. - [WhatsApp Business Platform](https://omnichannels.ai/glossary/whatsapp-business-platform/): The WhatsApp Business Platform is Meta's umbrella offering for businesses that message customers on WhatsApp through APIs, including the Cloud API, the Business Management API, the Marketing Messages API and related tools such as Flows, catalogs and webhooks. - [WhatsApp catalog](https://omnichannels.ai/glossary/whatsapp-catalog/): A WhatsApp catalog is a structured inventory of products or services, connected to a WhatsApp Business Account, that customers can browse, add to a cart and order from inside a WhatsApp chat. - [WhatsApp Flows](https://omnichannels.ai/glossary/whatsapp-flows/): WhatsApp Flows is a WhatsApp Business Platform feature for building structured, multi-screen forms inside a chat, such as bookings, lead forms, surveys or loan applications. The screens are defined in Flow JSON and can call the business's own endpoint. - [WhatsApp messaging limits](https://omnichannels.ai/glossary/messaging-limits/): WhatsApp messaging limits cap how many unique users a business portfolio can message outside customer service windows in a moving 24-hour period. According to Meta's documentation, the tiers are 250, 2,000, 10,000, 100,000 and unlimited. ## RCS - [Carousel (RCS)](https://omnichannels.ai/glossary/carousel/): An RCS carousel is a horizontally scrolling set of rich cards sent as one RCS Business Messaging message, so a user can compare several products, plans or options. Google's documentation allows a minimum of two and a maximum of ten cards. - [Google Jibe](https://omnichannels.ai/glossary/jibe/): Google Jibe is Google's RCS platform for mobile operators. It provides a hosted RCS backend that carriers can use instead of running their own, and an interconnect hub that links RCS networks so messages flow between operators. - [GSMA Universal Profile](https://omnichannels.ai/glossary/universal-profile/): The GSMA Universal Profile is the common RCS specification that carriers, device makers and messaging apps implement so RCS works the same way across networks and phones. Version 3.0 added end-to-end encryption based on Messaging Layer Security (MLS). - [RBM agent](https://omnichannels.ai/glossary/rbm-agent/): An RBM agent is the branded conversational entity that represents a business in RCS Business Messaging. It has a name, logo, colour, description and contact details, and it sends and receives messages for the brand through Google's RBM API. - [RCS](https://omnichannels.ai/glossary/rcs/): RCS (Rich Communication Services) is the GSMA standard that upgrades native phone messaging beyond SMS, adding typing indicators, read receipts, high-resolution media, group chat and, for businesses, branded and interactive messages. It runs over mobile data or Wi-Fi. - [RCS Business Messaging (RBM)](https://omnichannels.ai/glossary/rcs-business-messaging/): RCS Business Messaging (RBM) is the business side of RCS. Verified brands send branded, interactive messages, such as rich cards, carousels and suggested replies, to users' native messaging app through an RBM agent and Google's RBM API. - [RCS on iPhone](https://omnichannels.ai/glossary/apple-rcs/): RCS on iPhone is Apple's support for RCS messaging in the Messages app, introduced with iOS 18. iPhone users can exchange RCS chats, shown in green bubbles, with Android users when their carrier supports RCS on iPhone. - [Rich card](https://omnichannels.ai/glossary/rich-card/): A rich card is an RCS Business Messaging message that combines media (image, GIF or video), a title, a description and up to four suggested replies or actions in one card. It is used to present a product, offer or booking with clear next steps. - [Suggested replies and actions](https://omnichannels.ai/glossary/suggested-replies/): Suggested replies and actions are tappable chips in RCS Business Messaging. A reply sends predefined text back to the business. An action triggers a device function such as opening a URL, dialling a number, sharing a location or adding a calendar event. ## Compliance - [Do-not-disturb (DND) registry](https://omnichannels.ai/glossary/dnd-registry/): A do-not-disturb (DND) registry is a national or operator-run list of phone numbers whose owners have chosen not to receive marketing calls or messages. Senders must check, or have their provider check, numbers against it before promotional campaigns. - [Opt-in consent](https://omnichannels.ai/glossary/opt-in/): Opt-in consent is a recipient's clear, recorded permission to receive messages from a business on a given channel, captured before the first message is sent and stored with evidence such as the source, timestamp and wording shown. - [Opt-out](https://omnichannels.ai/glossary/opt-out/): An opt-out is a recipient's request to stop receiving messages from a business, usually by replying a keyword such as STOP (or ايقاف in Arabic) or tapping an unsubscribe button. The business must honour it promptly and suppress the number from future campaigns. - [Quiet hours](https://omnichannels.ai/glossary/quiet-hours/): Quiet hours are the times of day when promotional messages may not be sent to recipients, set by regulators, operators or a business's own policy. Transactional messages such as OTPs and alerts are normally exempt. ## Email - [Email deliverability](https://omnichannels.ai/glossary/email-deliverability/): Email deliverability is the ability of a sender's email to reach recipients' inboxes rather than being rejected or filtered to spam. It depends on authentication, sender reputation, list quality, complaint rates and content. - [SPF, DKIM and DMARC](https://omnichannels.ai/glossary/spf-dkim-dmarc/): SPF, DKIM and DMARC are the three DNS-based email authentication standards. SPF lists which servers may send for a domain, DKIM signs messages cryptographically, and DMARC tells receivers what to do when mail fails them and sends reports back. ## APIs and developers - [MCP server](https://omnichannels.ai/glossary/mcp-server/): An MCP server exposes tools, data and prompts to AI applications through the Model Context Protocol (MCP), an open standard, so an AI agent or assistant can discover and call those capabilities, for example sending a message, without custom integration code. - [One-time password (OTP)](https://omnichannels.ai/glossary/otp/): A one-time password (OTP) is a short code that is valid for a single login or transaction, usually for a few minutes. Businesses send it by SMS, WhatsApp, voice or email, or generate it in an authenticator app, to verify that the user controls a number, inbox or device. - [REST API](https://omnichannels.ai/glossary/rest-api/): A REST API is a web interface that exposes resources, such as messages, contacts or templates, at URLs and lets programs create, read, update and delete them with standard HTTP methods (POST, GET, PATCH, DELETE), usually exchanging JSON. - [SMS API](https://omnichannels.ai/glossary/sms-api/): An SMS API is a web interface, usually REST over HTTPS with JSON, that lets software send SMS, receive replies and get delivery statuses programmatically, without managing telecom connections directly. - [Two-factor authentication (2FA)](https://omnichannels.ai/glossary/two-factor-authentication/): Two-factor authentication (2FA) requires two different kinds of proof to sign in or approve an action: typically something you know (a password) plus something you have (a phone receiving a one-time code, an authenticator app or a security key). - [Webhook](https://omnichannels.ai/glossary/webhook/): A webhook is an HTTP request that a platform sends to a URL you provide whenever an event happens, such as a message being delivered, read or failed, or a customer reply arriving, so your system learns about it immediately without polling.