> ## Documentation Index > Fetch the complete documentation index at: https://apidoc.mailercloud.com/llms.txt > Use this file to discover all available pages before exploring further. # Add a Domain > Add a sending domain to your account and get the DNS records to publish at your DNS provider. The domain goes through exactly the same checks as **Account Settings → Domains** in the app (format, blocked and ISP domains, subdomain depth, duplicates and your plan's domain limit), and the same DNS records are generated. After adding the records at your DNS provider, verify the domain from **Account Settings → Domains**. **Notes** - The domain is case-insensitive and a leading `www.` is removed (`WWW.Example.com` is saved as `example.com`). - Subdomains up to 3 levels below the root are allowed (`news.example.com`, `a.b.c.example.com`). - Adding a domain can take a few seconds while its DNS is checked. ## OpenAPI ````yaml /openapi-v1.json post /domains openapi: 3.1.0 info: title: Mailercloud Marketing API version: 1.0.0 description: >- Campaigns, contacts, lists, segments, automations, and webhooks for the Mailercloud Marketing Platform. servers: - url: https://cloudapi.mailercloud.com/v1 security: - apiKey: [] tags: - name: Campaigns - name: Contacts - name: Lists - name: Tags - name: Segments - name: Custom Properties - name: Senders - name: Domains - name: Templates - name: Automations - name: Webhooks - name: Webforms - name: Inbox Tracker - name: Account paths: /domains: post: tags: - Domains summary: Add a Domain description: >- Add a sending domain to your account and get the DNS records to publish at your DNS provider. The domain goes through exactly the same checks as **Account Settings → Domains** in the app (format, blocked and ISP domains, subdomain depth, duplicates and your plan's domain limit), and the same DNS records are generated. After adding the records at your DNS provider, verify the domain from **Account Settings → Domains**. **Notes** - The domain is case-insensitive and a leading `www.` is removed (`WWW.Example.com` is saved as `example.com`). - Subdomains up to 3 levels below the root are allowed (`news.example.com`, `a.b.c.example.com`). - Adding a domain can take a few seconds while its DNS is checked. operationId: add-a-domain parameters: - name: Content-Type in: header required: true description: Request body type schema: type: string default: application/json requestBody: required: true content: application/json: schema: type: object required: - domain properties: domain: type: string description: >- The domain or subdomain to send from. Minimum: 3 Maximum: 100 Letters, digits, `-` and `.` only; a label must not start or end with `-`, and the last label must start with a letter. minLength: 3 maxLength: 100 examples: Domain: value: domain: example.com Subdomain: value: domain: news.example.com responses: '201': description: Created content: application/json: schema: type: object properties: message: type: string data: type: object properties: id: type: string description: Domain ID domainName: type: string description: The domain as saved (lowercased, without `www.`) addedMainDomain: type: string dmarc: type: string domainDetails: type: array description: DNS records to add at your DNS provider. items: type: object properties: data: type: string description: >- Record purpose: `track` (tracking), `dkim`, `dkim2`, `img` (images), `dmarc`, `haproxyval` (CAA — only when your existing CAA record would block certificate issuance) type: type: string description: '`CNAME`, `TXT` or `CAA`' name: type: string description: Host / name of the record value: type: string description: Value of the record show: type: integer description: '`1` = add this record' dnsStatus: type: string description: >- `2` = a conflicting record already exists (for example more than one DMARC record) examples: Example-1: value: message: >- The record of example.com successfully added to the ClouDns server, and domain created data: id: zjAKXb domainName: example.com addedMainDomain: example.com domainDetails: - data: track type: CNAME name: mc.example.com value: mc3035n.mlrcloud.com show: 1 - data: dkim type: CNAME name: k1._domainkey.example.com value: dkim.mlrcloud.com show: 1 - data: dkim2 type: CNAME name: k2._domainkey.example.com value: dkim2.mlrcloud.com show: 1 - data: img type: CNAME name: img3035n.example.com value: img3035n.mlrcloud.com show: 1 - data: dmarc type: TXT name: _dmarc.example.com value: >- v=DMARC1; p=reject; sp=none; adkim=s; aspf=s; rua=mailto:dmarc@mlrcloud.com; ruf=mailto:dmarc@mlrcloud.com; show: 1 '400': description: Bad Request — invalid input or the domain was refused content: application/json: schema: type: object properties: message: type: string errors: type: array items: type: object properties: field: type: string message: type: string examples: Invalid domain: value: message: Invalid domain Already exists: value: message: Your domain example.com already exists Already authenticated: value: message: Your domain example.com already authenticated ISP or disposable domain: value: message: >- Sorry! We block some major ISP domains due to their DMARC policy Blocked domain: value: message: >- Our anti-spam monitoring system blocked your domain. To be de-listed, contact us at support@mailercloud.com. Contains mailercloud: value: message: Domain cannot contain mailercloud Too many subdomain levels: value: message: Domain addition was unsuccessful due to domain hierarchy Plan limit: value: message: >- Free plan users can add only 1 domain. To add more domains, please upgrade your plan. In use by another account: value: message: >- The domain is already in use with another account. Please contact our support team for further assistance. Missing body: value: errors: - field: '' message: Invalid input '401': description: Unauthorized content: application/json: schema: type: object properties: errors: type: array items: type: object properties: field: type: string message: type: string examples: Example-1: value: errors: - field: '' message: Authorization failed '429': description: Too Many Requests content: application/json: schema: type: object properties: message: type: string examples: Example-1: value: message: Too Many Requests '500': description: Internal Server Error content: application/json: schema: type: object properties: message: type: string examples: Example-1: value: message: >- Sorry, we are experiencing some technical difficulties. Please try after some time. components: securitySchemes: apiKey: type: apiKey in: header name: Authorization description: >- Your Mailercloud API key (plain text, no Bearer prefix). Create keys in Settings → API. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.