01
Your app
Any SMTP client, any framework.
Node · Python · Ruby · Go · PHP · curl
One SMTP endpoint.
Every provider.
Verified before the send.
Autoresponders parsed for contacts.
sendrules is a multi-tenant SMTP proxy that routes across your existing providers, blocks bad recipients in the send path, harvests contacts from autoresponder replies, and gives you the deliverability tooling most vendors sell separately.
sendrules · pipeline
how it works01
Your appany SMTP client
NodePythonRubyGo
02
SMTP ingresssmtp.sendrules.net
587 STARTTLS465 implicitIP allow-list
03
Quality gate6 checks
SyntaxSuppressionDisposableRoleTypoLive SMTP
04
Grid & Rules6 strategies
RRWeightedPriorityStickyMX-ISP+ ramp-up
05
Provider fleet15 providers
SESSendGridPostmarkMailgun+11
06
Recipient inboxdelivery + replies
GmailYahooOutlookAppleOther
07
Autoresponder parserOOO → contacts
HarvestRegex fieldsIgnoreWebhookCSV
08
Signals & controlobservability
DMARCPostmasterBlocklistsHMAC webhooksActivity
15
providers supported end-to-end
6
routing strategies, one endpoint
11
pre-send checks in the SMTP DATA phase
How it works
Eight stages between your sendMail() and their inbox.
Verified, routed, delivered — then replies harvested for contacts you would otherwise lose.
02
SMTP ingress
smtp.sendrules.net, 587 STARTTLS + 465 implicit.
AUTH LOGIN/PLAINIP allow-listReal LE cert
03
Quality gate
Every recipient scored in the DATA phase.
SyntaxSuppressionDisposableRoleTypoLive SMTP
04
Grid & Rules
Pick a strategy. Fail over automatically.
RRWeightedPriorityRandomStickyMX-ISP
05
Provider fleet
Your accounts. Your reputation. Your quota.
SESSendGridPostmarkMailgun+11 more
06
Recipient MX
Gmail, Yahoo, Outlook, Apple, or anywhere else.
DeliveryBounceComplaintReplyOOO
07
Autoresponder parser
Turns OOO replies into contact lists — new colleagues, referrals, forwarded contacts.
Harvest emailsRegex fieldsIgnore listWebhookCSV export
08
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
01Any SMTP client, any framework.
Node · Python · Ruby · Go · PHP · curlSMTP ingress
02smtp.sendrules.net, 587 STARTTLS + 465 implicit.
AUTH LOGIN/PLAINIP allow-listReal LE certQuality gate
03Every recipient scored in the DATA phase.
SyntaxSuppressionDisposableRoleTypoLive SMTPGrid & Rules
04Pick a strategy. Fail over automatically.
RRWeightedPriorityRandomStickyMX-ISPProvider fleet
05Your accounts. Your reputation. Your quota.
SESSendGridPostmarkMailgun+11 moreRecipient MX
06Gmail, Yahoo, Outlook, Apple, or anywhere else.
DeliveryBounceComplaintReplyOOOAutoresponder parser
07Turns OOO replies into contact lists — new colleagues, referrals, forwarded contacts.
Harvest emailsRegex fieldsIgnore listWebhookCSV exportSignals & control
08Everything logged, signed, and searchable.
HMAC webhooks7-inbox ActivityDMARC ruaPostmaster
The problem
Sending isn’t a provider problem. It’s a routing problem.
Every ESP has an incident window, a throttle policy, and a reputation you don’t fully control. Locking yourself to one of them means one bad afternoon takes your transactional stream with it. sendrules sits in front of the providers you already trust and turns them into a fleet with observable routing, per-recipient verification, and shared deliverability tooling.
Bring your own
Bring the providers you already trust. We don’t resell sending.
Attach SES, SendGrid, Postmark, Mailgun, SparkPost, Brevo, Resend, Mailjet, Elastic, SMTP2GO, Zoho, Google Workspace, O365, Mailcrux, or any custom SMTP. Keep their pricing. Keep their warmed IPs. Keep the sender reputation you’ve spent years building. sendrules adds routing, verification, and observability without asking you to migrate a single domain.
AWS SESAPISendGridMailgunAPIPostmarkSparkPostAPIBrevoResendMailjetElastic EmailSMTP2GOZoho ZeptoMailGoogle WorkspaceOffice 365MailcruxCustom SMTP
Compatible with the providers you already use — bring your own credentials, keep your reputation.
Headline capability
Verify recipients before the send, not after the bounce.
Every recipient runs through syntax parsing, suppression lookup, disposable-domain detection, role-address flagging, typo correction, and a live SMTP mailbox check — inside the DATA phase, before your provider ever sees the address. Bounces you would have paid for become route logs you can act on. List decay becomes visible instead of expensive.
- Executed in-band; no pre-flight API call to remember
- Per-check block reasons written to the recipient's route log
- Rejected recipients do not count against monthly volume
Quality gate — RCPT
Syntaxvalid
Suppressionclean
Disposable domainnot listed
Role accountn/a
Typo detectiondid you mean example.com?
SMTP probedomain does not exist
550 5.1.2 recipient rejected · typo suggested · not counted against volume
Grid & Rules
Six routing strategies, one endpoint.
A Grid is a named routing rule with any number of providers attached. Pick round-robin, weighted, priority, random, sticky-sender, or MX-based ISP routing. Coverage warnings tell you which mailbox providers a Grid can actually reach before you save it. Temporary provider errors trigger automatic failover without touching your application code.
Round-robin, weighted, priority
Spread load evenly, distribute by weight, or fall through by priority until a provider accepts. Failover on temporary errors is automatic.
Sticky-sender
Pin every recipient to the first provider that delivered to them. Improves inbox placement over the second week without any manual list segmentation.
MX-based ISP routing
Resolve each recipient's live MX record and route on that — so vanity domains on Google Workspace or O365 land in the right ISP lane every time.
Automated warm-up
Ramp new sending mailboxes on an auto or manual schedule. Bounce and complaint thresholds trip a safety hold before the reputation damage lands.
Warm-up →MX-based classification
Route by the recipient’s real mail server.
Domain-string classification breaks the moment a customer moves acme.com to Google Workspace or O365. sendrules resolves the recipient’s live MX record and routes on that — so vanity domains land in the right ISP lane and your Gmail-tuned provider actually handles Gmail-hosted mail.
Deliverability suite
Deliverability tooling, alongside the sending it belongs to.
Aggregate ruaingest with per-source breakdowns. SPF, DKIM, and DMARC checked and graded A through F. Google Postmaster Tools pulled directly into per-domain views. Blocklist monitoring and seed-list inbox-placement testing on the domains you actually send from. One place to answer “why did that campaign underperform,” instead of four browser tabs.
DMARC monitoring
Aggregate rua ingest with per-source and per-IP breakdowns.
Learn moreAuth check
SPF, DKIM, DMARC — parsed, validated, graded A through F.
Learn morePostmaster Tools
Google reputation, spam rate, delivery errors — per domain.
Learn moreBlocklists + seeds
Continuous blocklist watch. Seed-list inbox placement on demand.
Learn moreInbound & replies
Managed reply addresses, without running your own MX.
Every rule can send with a plus-addressed replies.sendrules.net address that correlates a reply back to the original message. Choose what happens next — off, POST to a webhook, or land in a managed inbox you can browse in-app. Replies, bounces, and out-of-office are classified at ingest; the inbox forward-webhook can post the parsed message plus every email address found in the body to your own endpoint.
Managed inboxes
Point a reply address at an in-app inbox — read replies, extract contacts, or hand them to your own workflow later.
Inbound flow →Reply webhooks
Per-rule reply mode = webhook posts a JSON payload with the parsed reply + rule id + in-reply-to correlation, HMAC-signed with retries.
Bounce + OOO classified
Ingest classifies each inbound message — reply, hard bounce, soft bounce, out-of-office, unsubscribe — before it reaches your workflow.
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 emailsEvery address inside the body is extracted — new colleagues, forwards, referrals, procurement contacts.
- Named field captureRegex rules pull structured data — a name after 'Please contact', a phone number, an alternate ID.
- Ignore listSkip your own domain, common noise, and addresses you already have. Nothing duplicated, nothing polluted.
- Webhook or CSVPush new contacts into your CRM in real time, or download the list on demand.
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
- [email protected]procurement
- [email protected]legal
- [email protected]on leave
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"
}Observability
Every recipient. Every provider tried. Every reason blocked.
Activity splits into seven filtered inboxes — All, Delivered, Deferred, Bounced, Complained, Suppressed and Blocklisted, and Events. Row-level sparklines, period comparison against yesterday, last week, and last month, saved views, a column picker, keyboard shortcuts (/ r s ?), and anonymous read-only share links for anyone you need to hand a route log to.
Integration
Point your existing code at smtp.sendrules.net.
Standard SMTP submission on 587 with STARTTLS or 465 with implicit TLS, real Let’s Encrypt certificate. No SDK required — your existing SMTP client works today. When you need programmatic control, the REST API and event webhooks below cover everything the app UI does.
import nodemailer from "nodemailer";
const t = nodemailer.createTransport({
host: "smtp.sendrules.net",
port: 587,
secure: false, // STARTTLS
auth: {
user: process.env.SR_USER,
pass: process.env.SR_PASS,
},
});
await t.sendMail({
from: "[email protected]",
to: "[email protected]",
subject: "Hello from sendrules",
text: "Routed through your provider fleet.",
});Programmatic control
Manage providers, rules, ramps, inboxes, suppression lists, and DMARC domains via secure API keys. Every UI action has a corresponding endpoint — automate what your team does today.
See the platform →Event webhooks
Delivered, bounced, complained, opened, clicked, replied, and provider health changes. HMAC-signed, retried with backoff, replayable from the deliveries log.
Webhooks →External forward URLs
Point an inbox or a parser at your own HTTP endpoint. sendrules POSTs each parsed message and any addresses harvested from the body.
Inbound flow →Governance & controls
Roles, teams, audit — built in, not a Business-tier upsell.
Every mutation writes an audit row against the actor. Roles are a proper matrix — 30 resources, view/create/edit/delete/action verbs — with owner + admin + member defaults and custom roles per workspace. Teams group members for permission grants. Compliance work is credible when the platform captures the evidence for you.
Teams & custom roles
Group members into teams; grant a curated permission set to each. Owner is short-circuit allow so an org can never lock itself out.
Security overviewFine-grained permissions
Access-rights matrix covers every resource — providers, rules, ramps, DMARC, quality settings, retention, webhooks, API keys — with per-action granularity.
Complete audit log
Settings → Logs shows the full audit trail with actor, action, resource, IP, and metadata. System log surfaces control-plane errors alongside it.
Pricing
Public pricing. Real per-1k rates. All the way up.
Sandbox is free. Route from £15/mo annually for 100,000 emails. Fleet from £63/mo annually for 500,000. Command from £199/mo annually for 2M. Enterprise publishes a per-1k rate in your contract instead of “contact for pricing.”