> ## Documentation Index > Fetch the complete documentation index at: https://developer.lemlist.com/llms.txt > Use this file to discover all available pages before exploring further. > Sends an SMS message to a contact through the lemlist inbox. # Send SMS Message ## OpenAPI ````yaml post /inbox/sms openapi: 3.0.0 info: title: lemlist API version: 1.0.0 description: >- Welcome to the lemlist Developer Documentation. lemlist is very customizable and open. You'll find on this page all the API and integration you can do with lemlist. # Rate Limit lemlist's API rate limits requests in order to prevent abuse and overload of our services. Rate limits are applied on all routes and per API key performing the request. The rate limits are **20** requests per **2** seconds. The response provides any information you may need about it: | Header | Description | | --- | --- | | Retry-After | The number of seconds in which you can retry | | X-RateLimit-Limit | The maximum requests in that time | | X-RateLimit-Remaining | The number of remaining requests you can make | | X-RateLimit-Reset | The date when the rate limit will reset | _Example of values for the rate limit headers_ ``` json { "Retry-After": 2, "X-RateLimit-Limit": 20, "X-RateLimit-Remaining": 7, "X-RateLimit-Reset" : "Tue Feb 16 2021 09:02:42 GMT+0100 (Central European Standard Time)" } ``` # Definitions ## Team A team is the entity of lemlist that can handle users and billing. ## Credits Credits are the coins a team uses to enrich emails, LinkedIn URLs, etc. via the enrich route. Each enrichment feature needs a certain amount of credits to run. ## User You use a user account to connect to lemlist and send messages via the connected emails or LinkedIn account. ## Campaign A campaign is the entity to automate outreach. A campaign has multiple sequences composed of steps. ## Lead A lead is a person that you try to contact via a campaign. ## Activity An activity is the history of all the steps. ## Unsubscribe An unsubscribe occurs when a person decides they don't want to receive emails from you anymore. # Authentication All API routes use the dedicated subdomain `api.lemlist.com`. lemlist uses API keys to allow access to the API. You can get your lemlist API key at our [integration page](https://app.lemlist.com/settings/integrations). You need to add the `Authorization` header using the `Basic` authentication type. `login:password` **where the login is always empty and the password is the API key**. ⚠️ **Don't forget to add the semicolon (**`:`**) before your API key in curl command.** > To authorize, use this code: ``` shell curl https://api.lemlist.com/api/team \ --user ":YourApiKey" ``` **Make sure to replace** **`YourApiKey`** **with your API key.** # Give feedback If you want to report a bug, ask for data, or share with us a use case, please fill this [form](https://lemlist.typeform.com/to/mfVlkyGf). It will help us centralize your needs! servers: - url: https://api.lemlist.com/api security: - basicAuth: [] paths: /inbox/sms: post: tags: - Inbox summary: Send SMS Message description: >- Sends an SMS to a contact through the lemlist inbox. The message is sent to the contact's phone number (`phone` field, or the first entry of `phones`). Sending consumes SMS credits, one per message segment. parameters: [] requestBody: content: application/json: schema: type: object properties: sendUserId: type: string description: Sender user ID. Must belong to the team owning the API key. from: type: string description: >- Sender phone number, in E.164 format. Must be a phone number provisioned on your team; an unknown, pending or deleted number fails with `Failed to send SMS`. contactId: type: string description: >- Contact ID. Provide either contactId or leadId (not both required). Returned in the response. leadId: type: string description: >- Lead ID. Provide either contactId or leadId; when only leadId is sent, its contact is resolved and returned as contactId in the response. message: type: string description: >- SMS body. lemlist variables such as {{firstName}} are resolved against the contact before sending, and the resolved message must not be empty. required: - sendUserId - from - message example: sendUserId: usr_Example123UserAbc from: '+33612345678' contactId: ctc_Example123Contact message: Hi {{firstName}}, following up on our conversation responses: '200': description: Success content: application/json: schema: type: object properties: ok: type: boolean description: True when the SMS was sent. contactId: type: string description: >- The contact the SMS was sent to (resolved from leadId when only a lead was provided). example: ok: true contactId: ctc_Example123Contact '400': description: >- Possible errors: Bad team / Invalid sendUserId / contactId or leadId is required / Invalid leadId / Lead not found / Invalid contactId / Invalid message / Invalid from / Sender not found / The sender is not in the current team / Contact or lead not found (or has no valid email address) / Contact is unsubscribed / Variable is unsubscribed / SMS message body is empty / Failed to send SMS content: application/json: schema: type: object properties: error: type: string example: error: Bad team '401': description: The authentication you supplied is incorrect content: text/plain: example: The authentication you supplied is incorrect '402': description: Not enough SMS credits to send the message content: application/json: schema: type: object properties: error: type: string example: error: Not enough credit to send the sms '405': description: Method not allowed components: securitySchemes: basicAuth: type: http scheme: basic ````