Screen and triage invoice emails for approval with MailMint

Screen invoice emails and hold the doubtful ones for review with MailMint

Who's it for
Anyone whose accounts-payable inbox fills up with supplier invoices and who wants the routine ones to go straight through, but refuses to let a machine pay something it only half-understood. The interesting part is not the extraction — it is deciding, with reasons, which invoices a human still has to look at.

How it works

1. Receive the invoice email accepts a POST with the message you already have: subject, text and optionally html. Anything that can hand you an email works — the Gmail node, the Email Trigger (IMAP), a forwarding service, or a MailMint inbound address.
2. Set your approval policy is the one node you edit: the confidence you insist on, the amount a machine may approve on its own, the currency you expect, and whether the sender must be authenticated.
3. Is there an email to read? rejects an empty request before a parse is spent, so a broken payload gets a readable 422 instead of an empty result.
4. Read the invoice fields is MailMint. The fields are declared on the canvas — name, type, required, one line of description — and it returns each value with a confidence, the layer it came from, and the verbatim text it was read out of. With Route Messages Needing Review Separately switched on, the node has a second output: a required field it could not find, a value it could not coerce, or evidence it could not locate leaves by the lower branch, carrying the flag that says which. No IF node needed.
5. Score it against your policy does the real work, and every input is something you could check by hand: the lowest per-field confidence, whether each value has an evidence span, whether the required fields are actually there, the SPF/DKIM/DMARC verdicts, whether the amount is inside your ceiling, whether the currency is the expected one, and how many days are left until it is due.
6. Inside your policy? routes the result. Return it as approved answers 200 with the invoice, the lowest confidence and the days until due. Say why a human is needed answers 202 with the reasons — either the policy reasons or MailMint's own flags — plus the evidence, so a reviewer sees exactly what the machine saw.
7. If MailMint could not be reached, Explain what went wrong and Return the error as JSON answer 422 with the real failure text. The caller always gets an answer, and nothing is ever silently dropped.

How to set up

• Add a MailMint credential (free plan: 300 parsed emails a month, no card). The Base URL is already filled in.
• Put the four policy values in Set your approval policy.
• Activate the workflow and POST an invoice email to the production webhook URL.

Requirements

• A MailMint API key from mailmint.app.mintapis.com.
• ⚠️ This template uses a community node, so it runs on self-hosted n8n only.

How to customize
The schema in Read the invoice fields is a plain JSON list — add po_number, vat_rate or supplier_name and they appear in the output with their own confidence and evidence. The scoring in Score it against your policy is ordinary JavaScript: change a threshold, or add a rule of your own. Swap Return it for human review for a Slack, Jira or Notion node to file the doubtful ones where your team actually looks, and point Return it as approved at your accounting system.

Sender authentication
It is off by default, because a message posted to a webhook has no envelope to check. Switch it on when the mail arrives through a MailMint inbound address: there SPF, DKIM and DMARC are verdicts computed on the message as it was received, not guesses made afterwards — MailMint runs its own inbound SMTP server, so it sees the envelope and the raw bytes.

Disclosure
I build and run MailMint. This template is a self-submission, not a third-party recommendation.