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.
One SMTP endpoint.
Every provider.
Verified before the send.
sendrules is a multi-tenant SMTP proxy that routes across your existing providers, blocks bad recipients in the send path, and gives you the deliverability tooling most vendors sell separately.
sendrules · Grids
Today
12,481
+8%
This week
84,392
+21%
Delivered 7d
482,164
+14%
Grids
Marketing — EMEA
MX-based ISP · 4 providers · 500k/day
Active
Transactional prod
Priority + failover · 3 providers · unlimited
Active
Onboarding warm-up
Sticky sender · 2 providers · Day 12 / 300 → 5k
Warming
18:04:22 gmail.com · routed via SES · reason=isp_match · 234ms
15
providers supported end-to-end
6
routing strategies, one endpoint
4
verification checks in the SMTP DATA phase
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 Reacher SMTP-level verification — 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
Grids
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.
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.
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 moreObservability
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.
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.",
});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.”