Glossary
The vocabulary the Spaw API answers in, one term per page, each defined by what it means here rather than in general. Every entry names the field, verdict or reason it maps to and links to it.
- ASN
An Autonomous System Number identifies one network that announces its own routes to the internet under a single routing policy.
2026-09-10
- Address register
An address register is a country's official file of every address its authorities recognise, usually keyed on buildings rather than letterboxes.
2026-09-10
- CIDR
CIDR notation writes a range of IP addresses as one address and a prefix length, so 203.0.113.0/24 means the 256 addresses sharing those first 24 bits.
2026-09-10
- Catch-all domain
A catch-all domain is one whose mail server accepts mail addressed to every recipient, whether or not that mailbox exists.
2026-09-10
- Check digit
A check digit is a digit computed from the rest of an identifier so that a mistyped one usually fails arithmetic before anybody looks it up.
2026-09-10
- Company number
A company number is the identifier a national registrar assigns to an incorporated company, unique within that register and never within the world.
2026-09-10
- Credit
A credit is the billing unit of the whole API: one credit buys one fresh lookup that produced a usable answer, on any of the six signals.
2026-09-10
- Datacenter IP
A datacenter IP is an address inside a range operated by a hosting, cloud or server provider rather than by a consumer access network.
2026-09-10
- Delivery point
A delivery point is the smallest unit a postal service delivers to: one letterbox, one door, one box at a counter.
2026-09-10
- Disposable domain
A disposable domain is a mailbox provider handing out throwaway addresses that stop being read minutes or hours after they are created.
2026-09-10
- E.164
E.164 is the ITU-T standard that gives every phone number one unambiguous international form: a plus sign, a country calling code, and at most fifteen digits.
2026-09-10
- Greylisting
Greylisting is a mail server's habit of refusing an unfamiliar sender's first delivery attempt with a temporary error and accepting the retry.
2026-09-10
- Idempotency key
An idempotency key is a caller-chosen string sent with a create request so that a retry of the same request returns the original result instead of creating a second one.
2026-09-10
- Implicit MX
Implicit MX is RFC 5321's fallback: a domain with no MX record but with an A or AAAA record is treated as its own mail exchanger.
2026-09-10
- LEI
A Legal Entity Identifier is a 20-character code identifying a legal entity that takes part in financial transactions, defined by ISO 17442.
2026-09-10
- Line type
Line type is the kind of service a phone number was allocated for: mobile, fixed line, VoIP, toll-free, premium rate, shared cost and the rest.
2026-09-10
- MX record
An MX record is the DNS record naming a host that accepts mail for a domain, with a preference number that orders the candidates.
2026-09-10
- Mail drop
A mail drop is an address that exists to receive post for people and companies who are not there, such as a mail-forwarding branch or a formation agent.
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- Mailbox handshake
A mailbox handshake is an SMTP conversation opened with a domain's mail server as far as the RCPT TO step and abandoned before any message is sent.
2026-09-10
- NPA/NXX
NPA/NXX is the North American Numbering Plan's name for the first six digits of a US or Canadian number: the area code and the central office code.
2026-09-10
- Null MX
A null MX record is a single MX record with preference 0 pointing at the root, which is how a domain states in DNS that it accepts no mail at all.
2026-09-10
- PO box
A PO box is a numbered box rented at a postal facility, where mail is held for collection instead of being carried to a street address.
2026-09-10
- Postcode
A postcode is the code a postal service uses to sort mail to a delivery area, called a ZIP code in the United States, an Eircode in Ireland and a PIN in India.
2026-09-10
- Private mailbox
A private mailbox is a box rented at a commercial mail-receiving agency, written as a PMB or # number after that agency's own street address.
2026-09-10
- Request id
A request id is the identifier stamped on one API call, returned in the X-Request-Id header and repeated inside the response body.
2026-09-10
- Residential proxy
A residential proxy routes traffic through a real consumer connection so it looks like ordinary home traffic. Spaw does not detect them and says so.
2026-09-10
- Risk score
The risk score is a 0-100 number that is the sum of named signals with published weights, capped at 100 — not a model output.
2026-09-10
- Role address
A role address is a mailbox named for a function rather than a person: info@, support@, billing@, postmaster@.
2026-09-10
- Tor exit node
A Tor exit node is the last relay in a Tor circuit, the machine that makes the request to the destination on the user's behalf.
2026-09-10
- Unassigned block
An unassigned block is a range of numbers that a regulator's published allocation table shows as belonging to no operator.
2026-09-10
Try it on your own data
Every Spaw account gets 10 free credits at the start of each month, no card. One key answers every signal these pages describe, and the pricing page has every billing rule in full.