FirstSales Email API
Email address validation and risk checks.
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OpenAPI Specification
openapi: 3.2.0
info:
title: Firstsales Io Email API
version: 1.0.0
contact:
name: FirstSales Support
email: firstsales@support.communicate.so
url: https://firstsales.io
license:
name: Terms of Service
url: https://firstsales.io/terms-of-service/
termsOfService: https://firstsales.io/terms-of-service/
x-apiVersioning:
strategy: url-path
current: v1
pattern: https://firstsales.io/api/v1/{operation}
policyUrl: https://firstsales.io/developers/#versioning
note: A breaking change ships under a new prefix (/api/v2/); v1 keeps its contract. The unprefixed /api/{operation} form is an unversioned alias of the current version and may change without notice - call the /api/v1/ form.
x-deprecationPolicy:
minimumNoticeDays: 180
signalling: 'A deprecated version''s responses carry Deprecation: true and a Sunset header with the retirement date (RFC 8594), plus a Link rel="deprecation" to the migration notes.'
announcement: https://firstsales.io/developers/#deprecation-policy
policyUrl: https://firstsales.io/developers/#deprecation-policy
currentlyDeprecated: []
description: 'Operations tagged Email across 2 of this provider''s published API definitions: firstsales-io-openapi.json, openapi.json. Each path carries the servers of the definition it was published in.'
servers:
- url: https://firstsales.io
description: Production
security: []
tags:
- name: Email
description: Email address validation and risk checks.
paths:
/api/v1/email/validate:
post:
operationId: validateEmail
summary: Validate an email address's deliverability
description: 'Checks email format, then resolves the domain''s DNS to confirm it exists and has MX records, and flags reserved/disposable/free-provider domains. Use this before sending outreach to filter out addresses that cannot receive mail. Rate limit: 20 requests/minute per IP.'
tags:
- Email
security: []
x-rateLimit:
limit: 20
windowSeconds: 60
requestBody:
required: true
content:
application/json:
schema:
type: object
properties:
email:
type: string
format: email
required:
- email
responses:
'200':
description: Validation result (still 200 even when the email is invalid — check `valid`).
content:
application/json:
schema:
$ref: '#/components/schemas/EmailValidationResult'
'400':
description: Invalid request — bad input, missing field, or malformed value.
headers:
RateLimit-Limit:
description: Requests allowed in the current window.
schema:
type: integer
RateLimit-Remaining:
description: Requests still available in the current window.
schema:
type: integer
RateLimit-Reset:
description: Seconds until the current window resets.
schema:
type: integer
RateLimit-Policy:
description: Policy in the form "<limit>;w=<window seconds>".
schema:
type: string
content:
application/json:
schema:
$ref: '#/components/schemas/Error'
'429':
description: Rate limit exceeded for this endpoint. Wait Retry-After seconds and retry.
headers:
RateLimit-Limit:
description: Requests allowed in the current window.
schema:
type: integer
RateLimit-Remaining:
description: Requests still available in the current window.
schema:
type: integer
RateLimit-Reset:
description: Seconds until the current window resets.
schema:
type: integer
RateLimit-Policy:
description: Policy in the form "<limit>;w=<window seconds>".
schema:
type: string
Retry-After:
description: Seconds to wait before retrying.
schema:
type: integer
content:
application/json:
schema:
$ref: '#/components/schemas/Error'
'500':
description: Unexpected server error.
headers:
RateLimit-Limit:
description: Requests allowed in the current window.
schema:
type: integer
RateLimit-Remaining:
description: Requests still available in the current window.
schema:
type: integer
RateLimit-Reset:
description: Seconds until the current window resets.
schema:
type: integer
RateLimit-Policy:
description: Policy in the form "<limit>;w=<window seconds>".
schema:
type: string
content:
application/json:
schema:
$ref: '#/components/schemas/Error'
servers:
- url: https://firstsales.io
description: Production
/api/v1/email/disposable:
post:
operationId: checkDisposableEmail
summary: Score an email domain for disposable/temporary-mailbox risk
description: 'Runs six weighted checks (known disposable database, domain age via RDAP, MX validity, reputation, naming pattern, MX cross-reference) and returns a 0-100 score plus a safe/suspicious/disposable/high_risk classification. Use this to filter throwaway addresses out of a lead list. Rate limit: 20 requests/minute per IP.'
tags:
- Email
security: []
x-rateLimit:
limit: 20
windowSeconds: 60
requestBody:
required: true
content:
application/json:
schema:
type: object
properties:
email:
type: string
format: email
required:
- email
responses:
'200':
description: Disposable-risk assessment.
content:
application/json:
schema:
$ref: '#/components/schemas/DisposableCheckResult'
'400':
description: Invalid request — bad input, missing field, or malformed value.
headers:
RateLimit-Limit:
description: Requests allowed in the current window.
schema:
type: integer
RateLimit-Remaining:
description: Requests still available in the current window.
schema:
type: integer
RateLimit-Reset:
description: Seconds until the current window resets.
schema:
type: integer
RateLimit-Policy:
description: Policy in the form "<limit>;w=<window seconds>".
schema:
type: string
content:
application/json:
schema:
$ref: '#/components/schemas/Error'
'429':
description: Rate limit exceeded for this endpoint. Wait Retry-After seconds and retry.
headers:
RateLimit-Limit:
description: Requests allowed in the current window.
schema:
type: integer
RateLimit-Remaining:
description: Requests still available in the current window.
schema:
type: integer
RateLimit-Reset:
description: Seconds until the current window resets.
schema:
type: integer
RateLimit-Policy:
description: Policy in the form "<limit>;w=<window seconds>".
schema:
type: string
Retry-After:
description: Seconds to wait before retrying.
schema:
type: integer
content:
application/json:
schema:
$ref: '#/components/schemas/Error'
'500':
description: Unexpected server error.
headers:
RateLimit-Limit:
description: Requests allowed in the current window.
schema:
type: integer
RateLimit-Remaining:
description: Requests still available in the current window.
schema:
type: integer
RateLimit-Reset:
description: Seconds until the current window resets.
schema:
type: integer
RateLimit-Policy:
description: Policy in the form "<limit>;w=<window seconds>".
schema:
type: string
content:
application/json:
schema:
$ref: '#/components/schemas/Error'
servers:
- url: https://firstsales.io
description: Production
/api/v1/email/catchall:
post:
operationId: checkCatchAllDomain
summary: Detect whether a domain accepts mail to any mailbox (catch-all)
description: 'Sends live SMTP RCPT TO probes with random non-existent mailboxes at the domain''s primary MX host and infers catch-all behavior from acceptance/rejection. Use this to avoid false-positive ''valid'' verdicts on catch-all domains. Slower than the other email checks (real SMTP round-trips). Rate limit: 20 requests/minute per IP.'
tags:
- Email
security: []
x-rateLimit:
limit: 20
windowSeconds: 60
requestBody:
required: true
content:
application/json:
schema:
type: object
properties:
domain:
type: string
example: example.com
required:
- domain
responses:
'200':
description: Catch-all detection result.
content:
application/json:
schema:
$ref: '#/components/schemas/CatchAllResult'
'400':
description: Invalid request — bad input, missing field, or malformed value.
headers:
RateLimit-Limit:
description: Requests allowed in the current window.
schema:
type: integer
RateLimit-Remaining:
description: Requests still available in the current window.
schema:
type: integer
RateLimit-Reset:
description: Seconds until the current window resets.
schema:
type: integer
RateLimit-Policy:
description: Policy in the form "<limit>;w=<window seconds>".
schema:
type: string
content:
application/json:
schema:
$ref: '#/components/schemas/Error'
'429':
description: Rate limit exceeded for this endpoint. Wait Retry-After seconds and retry.
headers:
RateLimit-Limit:
description: Requests allowed in the current window.
schema:
type: integer
RateLimit-Remaining:
description: Requests still available in the current window.
schema:
type: integer
RateLimit-Reset:
description: Seconds until the current window resets.
schema:
type: integer
RateLimit-Policy:
description: Policy in the form "<limit>;w=<window seconds>".
schema:
type: string
Retry-After:
description: Seconds to wait before retrying.
schema:
type: integer
content:
application/json:
schema:
$ref: '#/components/schemas/Error'
'500':
description: Unexpected server error.
headers:
RateLimit-Limit:
description: Requests allowed in the current window.
schema:
type: integer
RateLimit-Remaining:
description: Requests still available in the current window.
schema:
type: integer
RateLimit-Reset:
description: Seconds until the current window resets.
schema:
type: integer
RateLimit-Policy:
description: Policy in the form "<limit>;w=<window seconds>".
schema:
type: string
content:
application/json:
schema:
$ref: '#/components/schemas/Error'
servers:
- url: https://firstsales.io
description: Production
components:
schemas:
MxRecord:
type: object
properties:
exchange:
type: string
priority:
type: number
required:
- exchange
- priority
Error:
type: object
description: Shared error envelope used by public endpoints and the rate-limit wrapper. Mail-tester handler errors use MailTesterError.
properties:
error:
type: string
description: Machine-readable error code, e.g. `invalid_input`.
message:
type: string
description: Human-readable explanation.
hint:
type: string
description: How to fix the request.
required:
- error
- message
- hint
CatchAllResult:
type: object
properties:
isCatchAll:
type: boolean
confidence:
type: string
enum:
- high
- medium
- low
checks:
type: array
items:
type: object
properties:
label:
type: string
status:
type: string
enum:
- pass
- warn
- fail
detail:
type: string
required:
- label
- status
- detail
score:
type: number
minimum: 0
maximum: 100
required:
- isCatchAll
- confidence
- checks
- score
EmailValidationResult:
type: object
properties:
valid:
type: boolean
domain:
type: string
domainExists:
type: boolean
hasMx:
type: boolean
isReserved:
type: boolean
isDisposable:
type: boolean
isFreeProvider:
type: boolean
mxRecords:
type: array
items:
$ref: '#/components/schemas/MxRecord'
error:
type: string
message:
type: string
required:
- valid
- domain
- domainExists
- hasMx
- isReserved
- isDisposable
- isFreeProvider
DisposableCheckResult:
type: object
properties:
score:
type: number
minimum: 0
maximum: 100
classification:
type: string
enum:
- safe
- suspicious
- disposable
- high_risk
checks:
type: array
items:
type: object
properties:
label:
type: string
status:
type: string
enum:
- pass
- warn
- fail
detail:
type: string
weight:
type: number
required:
- label
- status
- detail
- weight
details:
type: object
properties:
domain:
type: string
isDisposable:
type: boolean
domainAge:
type:
- object
- 'null'
properties:
registeredAt:
type: string
ageDays:
type: number
mxRecords:
type: array
items:
$ref: '#/components/schemas/MxRecord'
hasMx:
type: boolean
patternMatch:
type: boolean
databaseMatch:
type: boolean
required:
- score
- classification
- checks
- details
x-refined-from:
- firstsales-io-openapi.json
- openapi.json
x-apiVersioning:
strategy: url-path
current: v1
pattern: https://firstsales.io/api/v1/{operation}
policyUrl: https://firstsales.io/developers/#versioning
note: A breaking change ships under a new prefix (/api/v2/); v1 keeps its contract. The unprefixed /api/{operation} form is an unversioned alias of the current version and may change without notice - call the /api/v1/ form.
x-deprecationPolicy:
minimumNoticeDays: 180
signalling: 'A deprecated version''s responses carry Deprecation: true and a Sunset header with the retirement date (RFC 8594), plus a Link rel="deprecation" to the migration notes.'
announcement: https://firstsales.io/developers/#deprecation-policy
policyUrl: https://firstsales.io/developers/#deprecation-policy
currentlyDeprecated: []