@portable/spf

Functions

`Spf.check`

Checks whether an SMTP client may send mail for a domain, as RFC 7208's check_host() does. It reads the SPF record of the MAIL FROM domain, or of the HELO name when the sender is empty, and evaluates it against the client's IP address, with the RFC's limits of 10 DNS-querying terms and 2 void lookups. DNS failures give temperror, and broken records give permerror. The promise rejects only for an ip that isn't an IP address or a resolver without the Resolver methods, or with signal.reason when signal aborts.

async function check(
  input: check.Input,
  options: check.Options,
): Promise<Result>;

Option	Type	Default	Description
`resolver`	`Resolver`		Looks up DNS records. Pass `Dns.create()` or `node:dns/promises`.
`receiver`	`string`	`'unknown'`	The checking host's name, for `%{r}` in explanations.
`now`	`any`	`new Date()`	The time for `%{t}` in explanations, as a `Date` or a `Temporal.Instant`.
`signal`	`AbortSignal`		Rejects with `signal.reason` and cancels the pending lookups when aborted.

import * as Dns from '@portable/dns';
import * as Spf from '@portable/spf';
 
const spf = await Spf.check(
  {
    ip: '192.0.2.10',
    sender: 'alice@example.com',
    helo: 'mail.example.com',
  },
  { resolver: Dns.create(), signal: AbortSignal.timeout(20_000) },
);
spf.result; // 'pass', 'fail', 'softfail', 'neutral', 'none', 'temperror' or 'permerror'

Types

`Spf.Resolver`

The DNS lookups SPF needs: a Dns.Resolver from @portable/dns, node:dns/promises, or a plain object with these methods. check treats a rejection with code ENOTFOUND, ENODATA or EBADNAME (an invalid name) as an empty answer, and any other rejection as a temporary DNS error.

type Resolver = Pick<Dns.Resolver,  |  |  |  | >;

`Spf.Result`

The outcome of an SPF check.

type Result = {
    result: Result.Code;
    domain: string;
    identity:  | ;
    mechanism?: string | undefined;
    record?: string | undefined;
    explanation?: string | undefined;
    reason?: string | undefined;
    cause?: unknown;
    lookups: number;
    voidLookups: number;
};