How it Works

From `sendMail()` to
their inbox — and back.

Eight stages, one endpoint, every event logged. Below is the full journey — how one line of SMTP code becomes a verified, ISP-routed, provider-diversified send with a reply that comes back as a parsed contact.

Start free See it in production

Live pipeline · smtp.sendrules.net

Send

Verify

Route

Send

Land

Harvest

Verified · Routed · Delivered · Reply parsed← 8 stages in ≤ 240ms typical

How it works

Eight stages between your `sendMail()` and their inbox.

Verified, routed, delivered — then replies harvested for contacts you would otherwise lose.

Your app

Any SMTP client, any framework.

Node · Python · Ruby · Go · PHP · curl

SMTP ingress

smtp.sendrules.net, 587 STARTTLS + 465 implicit.

AUTH LOGIN/PLAINIP allow-listReal LE cert

Quality gate

Every recipient scored in the DATA phase.

SyntaxSuppressionDisposableRoleTypoReacher

Grid & Rules

Pick a strategy. Fail over automatically.

RRWeightedPriorityRandomStickyMX-ISP

Provider fleet

Your accounts. Your reputation. Your quota.

SESSendGridPostmarkMailgun+11 more

Recipient MX

Gmail, Yahoo, Outlook, Apple, or anywhere else.

DeliveryBounceComplaintReplyOOO

Autoresponder parser

Turns OOO replies into contact lists — new colleagues, referrals, forwarded contacts.

Harvest emailsRegex fieldsIgnore listWebhookCSV export

Signals & control

Everything logged, signed, and searchable.

HMAC webhooks7-inbox ActivityDMARC ruaPostmaster

Every step logged with reason codesHMAC-signed webhooks with replay4-tier limits — queue, don't dropDMARC + blocklist + Postmaster in one view

Your app
01
Any SMTP client, any framework.
Node · Python · Ruby · Go · PHP · curl
SMTP ingress
02
smtp.sendrules.net, 587 STARTTLS + 465 implicit.
AUTH LOGIN/PLAINIP allow-listReal LE cert
Quality gate
03
Every recipient scored in the DATA phase.
SyntaxSuppressionDisposableRoleTypoReacher
Grid & Rules
04
Pick a strategy. Fail over automatically.
RRWeightedPriorityRandomStickyMX-ISP
Provider fleet
05
Your accounts. Your reputation. Your quota.
SESSendGridPostmarkMailgun+11 more
Recipient MX
06
Gmail, Yahoo, Outlook, Apple, or anywhere else.
DeliveryBounceComplaintReplyOOO
Autoresponder parser
07
Turns OOO replies into contact lists — new colleagues, referrals, forwarded contacts.
Harvest emailsRegex fieldsIgnore listWebhookCSV export
Signals & control
08
Everything logged, signed, and searchable.
HMAC webhooks7-inbox ActivityDMARC ruaPostmaster

01Connect

One SMTP endpoint. Every language.

Point any SMTP client at smtp.sendrules.neton 587 (STARTTLS) or 465 (implicit TLS). AUTH LOGIN or AUTH PLAIN. Real Let’s Encrypt cert — no self-signed workarounds. Every credential can be scoped to a CIDR list so a leaked password from outside your infrastructure cannot authenticate.

Nodemailer, Django EmailMessage, Rails ActionMailer, PHPMailer, curl — anything that speaks SMTP
Credentials one-per-rule, so different traffic classes never share a queue
Rotate the password from the UI — the old one stops working immediately

import nodemailer from "nodemailer";

const t = nodemailer.createTransport({
  host: "smtp.sendrules.net",
  port: 587,
  secure: false,           // STARTTLS negotiated in-band
  auth: {
    user: process.env.SENDRULES_USER,   // per rule
    pass: process.env.SENDRULES_PASS,
  },
});

await t.sendMail({
  from: "[email protected]",
  to: "[email protected]",
  subject: "Your order #1042 is on its way",
  html: renderOrderEmail(order),
});

SMTP DATA · scoring 4 recipientsBudget · 2.0s

Syntaxpass
RFC-5322 shape, IDN-normalized
Suppression listpass
Global + per-tenant + auto-bounce ledger
Disposable domainreject
Union of curated + community feeds, refreshed daily
Role accountflag
info@ / admin@ / postmaster@ per policy
Typo domainflag
gmial.com → gmail.com suggested
Reacher SMTP verifypass
Live RCPT probe through rotating SOCKS5

accepted

flagged

rejected

03Verify

Six checks in the SMTP DATA phase.

Before the message ever leaves for a provider, every recipient is scored — inline, in the SMTP DATA phase itself, on a two-second budget. Bad addresses never spend your ESP quota. Risky ones are flagged. The policy is per-rule, so you can reject on outbound cold email and only flag on transactional.

Reacher-backed SMTP verify with a rotating SOCKS5 pool
Suppression ledger persists cross-tenant hard bounces — recycled spam-trap defense
Tiered cache (valid 30d / invalid 90d / catch-all 14d) so the same address is only probed once

Read the Quality Gate page

04Route

Six routing strategies. Coverage warnings built in.

Every rule picks a strategy. The rule editor tells you which ISPs your attached providers cover — and warns before you save if there’s a Yahoo-shaped gap.

Round-robin

Rotate through every attached provider evenly. Simple, predictable, hard to hurt yourself with.

Weighted

Assign a percentage per provider. 70% through SES, 25% through Postmark, 5% through the fallback.

Priority

Try provider one; if it errors, try provider two; and so on. The classical failover pattern.

Random

Uniform-random pick — useful for A/B testing two providers on identical traffic.

Sticky sender

First delivery to a recipient pins a sender. Every follow-up uses that same sender — reply-rate stays clean.

ISP

MX-based ISP

Resolve the recipient's live MX record. Gmail buyer → your Gmail-friendly provider; Yahoo → your Yahoo-friendly one.

Read the Grid & Rules page

05Send

Your accounts. Your reputation. Your quota.

sendrules holds your provider credentials sealed with AES-256-GCM per tenant, but never bills you for the mail — the send goes through your account with your provider. When one provider rate-limits or errors, the next attached provider picks up automatically.

Amazon SESok

1,842sent · last min

SendGridrate-limited

204sent · last min

Postmarkok

963sent · last min

Priority strategy — SendGrid returned 429, sendrules rerouted to Postmark on the same rule with no bounce, no drop.

06Land

Delivered — and classified by the real ISP.

We resolve the recipient’s live MX record, so “[email protected]” that fronts on Google Workspace is correctly routed as a Gmail recipient. Every provider webhook is normalized into the same event shape — delivered, bounced, complained, deferred — with the underlying provider preserved for drilldown.

MX-based classification catches domains that front on Google Workspace or Microsoft 365
Provider webhooks normalized to one event shape — no per-vendor branching in your app
Deferred sends land back in the queue with a retry-at timestamp; no dropped mail

Last 24h · classified by MX52,481 messages

Gmail62%
Outlook / Hotmail18%
Yahoo9%
Apple iCloud6%
AOL2%
Other3%

MX-based— we resolve the recipient’s live MX record, so “[email protected]” that fronts on Google Workspace is correctly counted as Gmail.

Autoresponder harvest

Every OOO reply is a contact. Most senders throw them away.

Ten to twenty percent of campaign replies are autoresponders — and most of them carry the exact contact info you were trying to reach: “I’m on leave until Monday, please contact [email protected] for procurement questions.” sendrules parses every one, harvests every address, captures every named field, and drops the result into a list you can trigger a webhook from or download as CSV.

Harvest emails
Every address inside the body is extracted — new colleagues, forwards, referrals, procurement contacts.
Named field capture
Regex rules pull structured data — a name after 'Please contact', a phone number, an alternate ID.
Ignore list
Skip your own domain, common noise, and addresses you already have. Nothing duplicated, nothing polluted.
Webhook or CSV
Push new contacts into your CRM in real time, or download the list on demand.

See the parser in the product Parser docs →

Inbound reply · 08:14 UTCAutoresponder · OOO

From: [email protected]

Subject: Automatic reply: Q4 vendor request

Thanks for your note — I’m on parental leave until 15 January 2026. For procurement, please reach [email protected]. Legal + contracts: [email protected] (direct: +44 20 7946 0123).

Parser: rule "acme-tier1" · list "acme-warm" · 3 new contacts

Contact list · acme-warm

1,247 totalExport CSV

Webhook · POST200 OK

{
  "event": "parser.contact",
  "list": "acme-warm",
  "email": "[email protected]",
  "fields": {
    "role": "procurement",
    "return_date": "2026-01-15"
  },
  "source_msg": "01f9...abcd",
  "ts": "2026-11-04T08:14:32Z"
}

Activity · live

AllDeliveredBounced

14:02:11delivered[email protected]Amazon SES
14:02:11delivered[email protected]Postmark
14:02:10opened[email protected]Amazon SES
14:02:09deferred[email protected]SendGrid → Postmark
14:02:08delivered[email protected]SES
14:02:07bounced[email protected]quality gate
14:02:06replied[email protected]inbound
14:02:05delivered[email protected]Postmark

98.2%

Delivery rate

0.4%

Bounce

0.02%

Complaint

08Observe

Every message, every step, every reason.

Seven filtered activity inboxes. Row-level sparklines. Period-comparison cards. Share links that make any filtered slice a public read-only URL. Behind it all: a normalized event stream your webhooks subscribe to, signed with HMAC-SHA256 and replayable from the UI.

Full deliverability suite alongside — DMARC compliance %, blocklist, Postmaster, seed placement
Saved views + column picker + keyboard shortcuts so Activity behaves like an inbox, not a report
Audit log on every operator action — RBAC-gated, regulator-ready

Under the flow

Six guarantees that hold under every stage.

STARTTLS + implicit TLS, real Let's Encrypt cert

AUTH restricted to your CIDR at the credential level

Message body sealed AES-256-GCM at rest

Every stage logged with a reason code

HMAC-SHA256 webhooks with retries and one-click replay

Four-tier limits — queue-don't-drop, midnight-UTC release

See the pipeline running against your own traffic.

Free plan — 5,000 messages/month, every feature on this page included. Attach one provider and watch the flow light up in the Activity view.

Start free See a live customer view

One SMTP endpoint. Every language.

Nodemailer, Django EmailMessage, Rails ActionMailer, PHPMailer, curl — anything that speaks SMTP

Credentials one-per-rule, so different traffic classes never share a queue

Rotate the password from the UI — the old one stops working immediately

import nodemailer from "nodemailer"; const t = nodemailer.createTransport({ host: "smtp.sendrules.net", port: 587, secure: false, // STARTTLS negotiated in-band auth: { user: process.env.SENDRULES_USER, // per rule pass: process.env.SENDRULES_PASS, }, }); await t.sendMail({ from: "[email protected]", to: "[email protected]", subject: "Your order #1042 is on its way", html: renderOrderEmail(order), });

Six checks in the SMTP DATA phase.

Reacher-backed SMTP verify with a rotating SOCKS5 pool

Suppression ledger persists cross-tenant hard bounces — recycled spam-trap defense

Tiered cache (valid 30d / invalid 90d / catch-all 14d) so the same address is only probed once

Read the Quality Gate page

Delivered — and classified by the real ISP.

MX-based classification catches domains that front on Google Workspace or Microsoft 365

Provider webhooks normalized to one event shape — no per-vendor branching in your app

Deferred sends land back in the queue with a retry-at timestamp; no dropped mail

Every OOO reply is a contact. Most senders throw them away.

Harvest emails

Every address inside the body is extracted — new colleagues, forwards, referrals, procurement contacts.

Named field capture

Regex rules pull structured data — a name after 'Please contact', a phone number, an alternate ID.

Ignore list

Skip your own domain, common noise, and addresses you already have. Nothing duplicated, nothing polluted.

Webhook or CSV

Push new contacts into your CRM in real time, or download the list on demand.

{ "event": "parser.contact", "list": "acme-warm", "email": "[email protected]", "fields": { "role": "procurement", "return_date": "2026-01-15" }, "source_msg": "01f9...abcd", "ts": "2026-11-04T08:14:32Z" }

Every message, every step, every reason.

Full deliverability suite alongside — DMARC compliance %, blocklist, Postmaster, seed placement

Saved views + column picker + keyboard shortcuts so Activity behaves like an inbox, not a report

Audit log on every operator action — RBAC-gated, regulator-ready

From sendMail() totheir inbox — and back.

Eight stages between your sendMail() and their inbox.

Your app

SMTP ingress

Quality gate

Grid & Rules

Provider fleet

Recipient MX

Autoresponder parser

Signals & control

Your app

SMTP ingress

Quality gate

Grid & Rules

Provider fleet

Recipient MX

Autoresponder parser

Signals & control

One SMTP endpoint. Every language.

Six checks in the SMTP DATA phase.

Six routing strategies. Coverage warnings built in.

Round-robin

Weighted

Priority

Random

Sticky sender

MX-based ISP

Your accounts. Your reputation. Your quota.

Delivered — and classified by the real ISP.

Every OOO reply is a contact. Most senders throw them away.

Every message, every step, every reason.

Six guarantees that hold under every stage.

See the pipeline running against your own traffic.

From sendMail() totheir inbox — and back.

Eight stages between your sendMail() and their inbox.

Your app

SMTP ingress

Quality gate

Grid & Rules

Provider fleet

Recipient MX

Autoresponder parser

Signals & control

Your app

SMTP ingress

Quality gate

Grid & Rules

Provider fleet

Recipient MX

Autoresponder parser

Signals & control

One SMTP endpoint. Every language.

Six checks in the SMTP DATA phase.

Six routing strategies. Coverage warnings built in.

Round-robin

Weighted

Priority

Random

Sticky sender

MX-based ISP

Your accounts. Your reputation. Your quota.

Delivered — and classified by the real ISP.

Every OOO reply is a contact. Most senders throw them away.

Every message, every step, every reason.

Six guarantees that hold under every stage.

See the pipeline running against your own traffic.

From `sendMail()` to
their inbox — and back.

Eight stages between your `sendMail()` and their inbox.

From `sendMail()` to
their inbox — and back.

Eight stages between your `sendMail()` and their inbox.