Soenneker.Validators.Yahoo.Exists 4.0.2677

Soenneker.Validators.Yahoo.Exists

Applies an undocumented Yahoo signup-response heuristic to a supplied address's local part.

Install

dotnet add package Soenneker.Validators.Yahoo.Exists

Registration

using Soenneker.Validators.Yahoo.Exists.Registrars;
using Microsoft.Extensions.DependencyInjection;

services.AddYahooExistsValidatorAsSingleton();

Scoped registration is also available. Both registrations reuse singleton HTTP-client-cache and rate-limiter-factory services. Disposing a scoped validator leaves the shared named HTTP client alive.

Configure request spacing

{
  "YahooExistsValidator": {
    "IntervalMs": 4000
  }
}

The default interval is 4,000 milliseconds. EmailExists executes through a shared named rate limiter using this spacing.

Check an identifier

using Soenneker.Validators.Yahoo.Exists.Abstract;

bool? result = await validator.EmailExists(
    "person@yahoo.com",
    cancellationToken);

The validator loads Yahoo's signup page, extracts session cookies and hidden state, then submits the text before the first @ as a proposed Yahoo user ID. It returns:

• true when Yahoo reports IDENTIFIER_NOT_AVAILABLE or IDENTIFIER_EXISTS for userId;
• false when the parsed response does not contain either marker;
• null when the required signup cookies or session index cannot be extracted.

HTTP failures, non-success status codes, response-deserialization failures, and cancellation propagate. EmailExistsWithoutLimit skips only the local rate limiter; it does not bypass Yahoo's limits.

The method does not validate email syntax or require a Yahoo domain. person@gmail.com and person@yahoo.com both query the Yahoo identifier person, while input without @ is submitted in full. Validate and normalize input before calling if that distinction matters.

Reliability and privacy

This uses an undocumented signup endpoint and page structure. Yahoo can change the cookies, HTML, API response, or blocking behavior without notice, producing errors or incorrect results. It is not proof that a mailbox is reachable or owned by a user; send a verification message for ownership.

The queried local part is disclosed to Yahoo. Full addresses are no longer included in this validator's logs, but request content may still appear in upstream HTTP infrastructure or Yahoo's logs. Ensure the check is compatible with privacy requirements and provider terms.