SPF Checker
Open SPF Checker on Happytails.ai. This view has the same page content and links, with explicit tool capabilities. Read the processing notes before using a tool.
Tool capabilities
{
"id": "spf-checker",
"category": "email-tools",
"built": true,
"requirements": "DNS lookups, include-chain limits and findings; never infer delivery guarantee.",
"implementation": {
"fields": [],
"processing": "Server required",
"note": "Uses the local diagnostic server to contact the supplied public host or DNS/RDAP provider. Only public internet addresses are permitted; requests time out and redirects are bounded.",
"experience": {
"automatic": false,
"single": true,
"inputMaxLength": 1000000,
"inputMode": "text",
"label": "Domain name",
"placeholder": "happytails.ai",
"help": "Enter one domain name without https://, a path or a port.",
"helpParts": [
"Enter one domain name without https://, a path or a port."
],
"action": "Check domain"
},
"mode": "explicit",
"interactive": false
},
"execution": "POST /api/v1/tools/spf-checker/run",
"api": {
"id": "spf-checker",
"name": "SPF checker",
"category": "email-tools",
"description": "DNS lookups, include-chain limits and findings.",
"notes": "Uses the local diagnostic server to contact the supplied public host or DNS/RDAP provider. Only public internet addresses are permitted; requests time out and redirects are bounded.",
"human_path": "/en/email-tools/spf-checker/",
"method": "POST",
"endpoint": "/api/v1/tools/spf-checker/run",
"schema_url": "/api/v1/tools/spf-checker",
"input_schema": {
"type": "object",
"additionalProperties": false,
"properties": {
"input": {
"type": "string",
"maxLength": 1000000,
"default": "",
"description": "Plain text input. File tools use files instead unless otherwise documented."
},
"options": {
"type": "object",
"additionalProperties": false,
"properties": {}
}
}
},
"output_schema": {
"type": "object",
"required": [
"tool",
"result"
],
"properties": {
"tool": {
"type": "string"
},
"result": {
"type": "object",
"required": [
"text",
"files"
],
"properties": {
"text": {
"type": [
"string",
"null"
]
},
"data": {
"description": "Parsed JSON when the textual result is JSON."
},
"name": {
"type": "string"
},
"mime": {
"type": "string"
},
"files": {
"type": "array",
"items": {
"type": "object",
"required": [
"name",
"mime",
"bytes",
"base64"
],
"properties": {
"name": {
"type": "string"
},
"mime": {
"type": "string"
},
"bytes": {
"type": "integer"
},
"base64": {
"type": "string",
"contentEncoding": "base64"
}
}
}
}
}
}
}
},
"processing": "Server; contacts public network services",
"limits": {
"request_bytes": 8388608,
"input_characters": 1000000,
"files_bytes": 5242880,
"max_files": 0,
"timeout_seconds": null
}
},
"agent_processing": "Server; contacts public network services",
"browser_agent": {
"supported": true,
"name": "run_current_tool",
"discovery": "WebMCP on the human page in a supporting browser",
"verification": "See audit/API-AUDIT.md; availability is not verification"
}
}Page guide
Check which mail servers a domain authorizes to send email.
This tool needs server processing
The public server is not connected yet. File selection and processing are unavailable on this website.
Browse other tools in this categoryHow to use SPF checker
- Enter a domain name in the input field.
- Review the settings, then choose Check domain.
- Review the result, then use Copy result or a download link when available.
Working with spf checker
Email tools can inspect addresses, message headers, templates and domain configuration. These tasks answer different questions: a syntactically valid address is not the same as a mailbox that exists, and a configured domain is not a guarantee of inbox placement.
Common questions
Does address validation prove a mailbox exists?
Syntax checks can catch formatting mistakes but cannot prove that a person receives mail at an address. Server-side checks can also be inconclusive.
Do authentication records guarantee inbox delivery?
No. Authentication is one signal among several. Sending behavior, recipient engagement and filtering rules also affect what happens to a message.