Mailcheck
Verify single or bulk email addresses via the Mailcheck API.
About
Mailcheck ships in the w6w first-party pack. It declares 4 actions, 1 health check, and the host runs its code in a sandbox that never sees the credential.
- App id
io.w6w.mailcheck- Version
- 0.1.3
- Author
- w6w
- Licence
- MIT
- Categories
- Email · Marketing
Overview
Mailcheck verifies email addresses from a workflow — checking a single address synchronously and getting back trust and deliverability signals, such as whether the domain accepts mail, whether it’s a disposable address, and whether it’s a catch-all, alongside best-effort identity hits like a matching Gravatar or GitHub username.
For larger volumes, a batch check runs as an async operation: submitted once, then polled or listed until it completes, which is the right shape for validating a list of addresses — a signup import, a marketing list — without checking each one inline and blocking on the result.
A fit for filtering out invalid or disposable addresses before adding them to a mailing list, gating a signup flow on a real-looking email, or cleaning an existing list in bulk.
Build with Mailcheck
Three routes to the same 4 actions. The Workflow tab is generated from Mailcheck's own manifest and carries its real ids, so it is copy-pasteable; the Code and CLI examples are the same call for any action on any app, so every app-specific value in them is a blank you fill in.
Get Batch Operation
batch-operation-get Read the status (and result, once finished) of a batch check operation.
List Batch Operations
batch-operation-list List batch check operations for the authenticated account.
A workflow step names the app and the action, and the editor fills in the
connection when you pick one. This is the Step shape from the
workflow spec, carrying Mailcheck's real ids.
{
"manifestVersion": "2",
"name": "mailcheck-example",
"steps": [
{
"id": "batch-check-create",
"uses": {
"app": "io.w6w.mailcheck",
"action": "batch-check-create",
"connection": "conn_YOUR_CONNECTION_ID"
},
"with": {
"emails": "<emails>"
}
}
]
}Here are some of the things you can do
-
Create Batch Check
performbatch-check-create -
Get Batch Operation
readbatch-operation-get -
List Batch Operations
readbatch-operation-list -
Check Email
readcheck-email
Every app-specific value here is a blank you have to fill in. An
app action is reached through the connection that authenticates it, so the
address is a connection id, not the app id — and connections belong to your account,
so a public page cannot know yours. Create one for Mailcheck, then fill in
the three blanks: conn_YOUR_CONNECTION_ID, the action key, and the
parameters that action declares. The call itself is real — the shape is transcribed
from the studio's own snippet builder, which prints the same kind of blanks — but
nothing in it is specific to Mailcheck. The Workflow tab is where this app's
real ids are.
npm install @w6w/sdkyarn add @w6w/sdkpnpm add @w6w/sdkdeno add npm:@w6w/sdkimport { W6wClient, isActionRun } from "@w6w/sdk";
// Reads W6W_BASE_URL and W6W_TOKEN from the environment when omitted.
const client = new W6wClient();
const envelope = await client.run({
urn: "conn_YOUR_CONNECTION_ID",
action: "check-email",
payload: {
email: "<value>",
},
});
if (isActionRun(envelope)) console.log(envelope.value);npm install -g @w6w/cliw6w run conn_YOUR_CONNECTION_ID --action check-email --payload '{"email":"<value>"}'Give an AI agent Mailcheck — without giving it Mailcheck's credentials. One MCP endpoint exposes every app, function and workflow the caller is entitled to, as tools it can discover and run. Access is granted per team while we onboard.
One tool call{
"name": "w6w_invoke",
"arguments": {
"ref": "app:io.w6w.mailcheck#batch-check-create",
"input": {
"emails": "<emails>"
}
}
}
Every tool names its target with a single ref. The
app: form above doesn't name a connection at all — the
host resolves which of the caller's Mailcheck connections to sign
with, and refuses rather than guesses when the answer is ambiguous.
What the agent gets
Credentials it can't read
The token is attached host-side, at the moment of the call. It is never a tool argument, never in the model's context, and never in a transcript — so a prompt injection has nothing to exfiltrate.
A tool surface scoped to the caller
Tools are derived per end user from what that person has actually connected and is entitled to — not one shared bot identity carrying the union of everyone's access.
A durable workflow in one call
Multi-step work runs on the workflow engine and returns a run handle the agent can poll — retries, branching and state survive the conversation that started them.
Health-aware discovery
Mailcheck's declared health checks are on the surface too, so an agent can tell "the vendor is down" from "your credential expired" before it burns a retry on either.
The MCP surface is part of the hosted platform. Mailcheck itself is MIT, and the runtime that executes it is source-available (FSL).
Health checks
Mailcheck declares its own checks, so its health is a property of the app rather than something the host guesses at.