Find and verify emails with alias resolution and multi-domain discovery. Map addresses to valid, existing identities.
Agent integration
Install the MCP server in your preferred coding agent and start running finder and probe calls from the same workspace token.
the old technique
Servers today have adapted to prevent SMTP probing and this technique began to yield worse results as time went by -- relying on it can only be effective ~50% of the time. Unlike most providers, Relentless Identity has developed a new method that doesn't depend on these probes only. For a shorter explanation, read about why SMTP verification falls short. It returns valid identities regardless of catch-all status, finds alternative domains, and resolves aliases; the most recent and effective tool for large SaaS databases and complex workloads.
While good tools exist, a pressing issue needed answering: Most results are imprecise and not accurate. Organizations adopting catch-all domain behavior and sitting behind gateways were increasing significantly. Relentless Identity is a modern, up-to-date response to all of this change. Read the clearer breakdown of identity verification vs. email verification if you want the decision rule in one place.
We're the only API that can reliably resolve detected aliases and find addresses across multi-domain organizations from a single, public-facing website domain.
How we compare
Most companies relying on email miss on average 25% of their revenue due to poor data. Our API is built to interpret modern identity and email infrastructure stacks to return live, accurate data; helping with fraud prevention, marketing efforts and underwriting.
| Capability | MillionVerifier | BounceBan | trykitt.ai | Relentless Identity |
|---|---|---|---|---|
| SMTP probing | ||||
| Catchall detection | ||||
| Precise Catchall Verification | ||||
| MCP-native access for AI agents | ||||
| Identity Provider Discovery | ||||
| Alias Detection and Resolution | ||||
| Multi-domain Identity Finder |
Identity coverage
Below are the identity providers we support
Why it resolves better
01
Results are produced from live provider and mailbox checks instead of stale dumps, recycled enrichment tables, or purchased address inventories. Only caching is used for redundant requests to optimize for speed.
02
SMTP probing can surface deliverability but it cannot reliably map a mailbox to a real identity once gateways, catch-all behavior, and modern login stacks get involved.
03
Relentless Identity correlates provider-side identity evidence with live routing signals, which is why it can resolve aliases and distinguish valid users from generic catch-all responses.
Built for modern outreach stacks
Relentless Identity is built for teams that need a reliable answer about a specific person, not just a mailbox verdict. Sales and RevOps teams use it to find the right work email before outreach. Recruiting teams use it to verify candidate contacts. Fraud, underwriting, and onboarding teams use it when an email needs to be tied back to a real identity rather than a generic deliverability score.
The product is also designed for technical workflows. Developers can call the REST API, agents can use MCP, and data pipelines can keep the same response semantics across find-and-verify steps. If you are deciding whether you need list hygiene or identity-level confidence, start with the identity verification vs. email verification guide.
API playground
API wrappers and MCP clients available for seamless integration with a compact response body
POST /client/attempt
How it works
1
Provide either a name, company domain pair or an email address.
2
Performs domain discovery before verifying against the person or given identity.
3
For finder calls, it'll look for related email domains and for an identity across them. For individual probe calls, it'll confirm whether the particular identity exists or not for the given email domain.
FAQ
It is a check that asks whether an address belongs to a real work identity, not just whether a mail server might accept a message. For more context, see the identity vs. email verification guide.
Catch-all domains accept mail broadly, so SMTP checks alone can be ambiguous. Relentless Identity combines provider, routing, and domain signals to narrow the result, and the gateway guide explains why this matters.
Finder starts with a person and a company domain, while Probe starts with a known email address. The Finder API workflow shows how the two steps fit together.
Yes. MCP is part of the core product surface, so agents and IDEs can run the same workflows as the API. Read the MCP workflows article for the implementation pattern.