Features that make mail hop, not stop
SMTP Hopper packs enterprise-grade relay reliability into a lightweight Windows service you can install before your coffee cools.
Durable queueing with smart retries
The moment SMTP Hopper accepts a message, it's written to disk. A background delivery worker then relays it upstream — and if your provider is briefly unreachable, backoff kicks in automatically.
- Write-to-disk first: a power cut or service restart never loses accepted mail.
- Exponential backoff: up to 8 delivery attempts with increasing delays.
- Dead-letter safety net: permanent (5xx) failures and exhausted retries are preserved for review — with the exact upstream error attached.
- Live queue view: watch pending, delivered, and dead-lettered messages in the admin console, including each message's last error.
A real admin console, not a config file
Everything is managed through a local HTTPS web GUI — from first-run setup to day-two operations. No registry edits, no XML surgery.
- Guided first-run setup: create your admin account and point at your provider in one pass.
- Relay user management: per-device credentials with enable/disable and one-click password resets.
- Connector & listener settings: hosts, ports, TLS modes — connector changes apply instantly, no restart.
- Structured log viewer: browse the relay's JSON logs right in the browser.
Locked down out of the box
SMTP Hopper is never an open relay. Every inbound connection must authenticate by default, and every credential is handled the way you'd hope.
- SMTP AUTH flexibility on every inbound connection.
- Trusted IP whitelist: devices that can't authenticate (many printers and legacy apps) can be allowed by exact IP or CIDR range — everyone else still authenticates. Changes apply instantly.
- bcrypt-hashed passwords for admin and relay-user logins — never stored or logged in plaintext.
- Sender rate limiting caps volume per credential to contain a leaked password's blast radius.
- Bring your own certificate: replace the self-signed TLS cert with your CA-issued or internal-PKI cert right from Settings.
Multi-instance sync for zero single points of failure
Run two or more SMTP Hopper instances behind a load balancer and let Sync keep them consistent — so a device authenticating against any instance just works.
- Peer-to-peer exchange replicates relay users and the trusted IP whitelist across instances.
- Improve throughput, keeps business running without hiccups.
- Avoids downtime allows for patching, maintenance, while mail keeps flowing.
- Load Balancer Health Probes lets the load balancers know whose up and whose down.
Analytics that answer "who's sending what?"
The Analytics page charts your mail flow over time and ranks your busiest senders — without ever storing message content.
- Usage over time: accepted, delivered, and dead-lettered messages across 24h, 7d, 30d, and 90d ranges.
- Top senders: which relay users (or whitelisted IPs) send the most, with message counts and total size.
- Inactive relay users helps keep the relay user list limited to only who is actively using it.
- Zero dependencies: all the data is kept local — perfect for isolated, internet-free networks.
Know exactly who got turned away — and why
The Refused Connections page lists the last 100 rejected sends, newest first, so misconfigured devices and probing strangers are never a mystery.
- Failed logins with the username that was tried and its source IP.
- Unauthorized senders not covered by a relay user or the IP whitelist.
- Oversized messages and protocol errors, captured best-effort.
- 90-day retention, and no message content is ever stored.
A first-class Windows citizen
SMTP Hopper installs, runs, and uninstalls like software your team already knows how to manage.
- Native Windows service with automatic crash recovery and staged restart delays.
- Easy installation — just install the EXE and let mail fly.
- Seemless upgrades, as simple as running the latest EXE while logs, configurations, all are kept safe.
- No coding or commands, means no bash, no powershell. Everything is done through the Web GUI.
- Web interface keeps everything running for years to come without any dependencies.
See every feature live, on your own network
Our team will walk you through setup, security, and HA — tailored to your environment.
Request a Demo