UK-based SMTP relay for IoT and M2M

Email alerts for IoT devices.
Built properly.

Dedicated SMTP relay for routers, sensors, gateways and M2M equipment. Per-device credentials. TLS enforced. Amazon SES backbone. Your devices send. Your alerts arrive.

Start free - 5 devices See how it works
587
STARTTLS port
465
SMTPS port
TLS 1.2+
Minimum enforced
SES
Relay backbone
UK
GDPR compliant
The problem
Consumer ISPs block port 25 Generic SMTP flags machine senders as abuse Shared relays damage your reputation One credential for all devices is a security risk No UK-based IoT SMTP service exists
How it works

Register. Add devices. Configure. Send.

IoTMail is self-serve. No sales calls, no waiting for account approval, no shared relay pools. You register, pick an account handle, add your devices, copy the credentials into your firmware, and you are live.

STEP 01

Register your account

Email and password. No card required for the free tier. Choose your account handle - this becomes the prefix for every device address on your account.

STEP 02

Add your devices

Name each device and assign a tag. IoTMail generates a unique SMTP username and password for each one. Credentials are system-generated - long, random, and not user-settable.

STEP 03

Configure your firmware

Copy smtp.iotmail.co.uk, port 587, username and password into your device. Takes about 30 seconds on a Teltonika or Milesight. Any device with standard SMTP AUTH support works.

STEP 04

Monitor in the portal

The portal shows delivery status, send logs, bounce reports and usage per device. Silence detection flags devices that have stopped sending - catching broken alert chains before they matter.

Sub-addressing model

Every device has its own traceable identity

IoTMail uses plus-addressing to embed device identity directly into the sender address. Recipients can filter, route, and audit by sender address alone. No changes needed to the receiving email infrastructure.

acme+gw-001@iotmail.co.uk
acme - your account handle, chosen at registration gw-001 - device identifier, set per device in portal iotmail.co.uk - verified sending domain, SPF + DKIM + DMARC
acme+gw-001@iotmail.co.ukTeltonika RUT241, Site A
acme+sensor-14@iotmail.co.ukMilesight CO2 sensor
acme+reboot-mon@iotmail.co.ukPing reboot watchdog
bigcorp+tower-0847@iotmail.co.ukEnterprise fleet device
Server-side validation: The device tag in the username and the From: address are validated on every single SMTP connection. An authenticated device cannot send as a different device. An unauthenticated device cannot send at all. This is enforced in the mail filter pipeline, not as an optional setting.
Pricing

Start free. Scale when you need to.

No hard cutoffs. Pro and Scale accounts run over their daily limit with a small per-email overage charge rather than going silent. A fleet doubling after a rollout must not stop sending alerts.

Starter
Free forever
No credit card
  • Devices 5
  • Emails / day 50
  • Log retention 7 days
  • TLS enforced Yes
  • SPF / DKIM / DMARC Yes
  • REST API No
  • Webhooks No
  • IP allowlist No
MOST POPULAR
Pro
£12 / month
Free 12 months for router customers
  • Devices 50
  • Emails / day 500
  • Log retention 30 days
  • TLS enforced Yes
  • SPF / DKIM / DMARC Yes
  • REST API Full
  • Webhooks Yes
  • IP allowlist Yes
Scale
£49 / month
 
  • Devices 500
  • Emails / day 5,000
  • Log retention 90 days
  • TLS enforced Yes
  • SPF / DKIM / DMARC Yes
  • REST API Full
  • Webhooks Yes
  • IP allowlist Yes
Enterprise
POA
Volume and SLA pricing
  • Devices Unlimited
  • Emails / day Unlimited
  • Dedicated IP Yes
  • Custom domain Yes
  • SSO / SAML Yes
  • RBAC Yes
  • SLA 99.9%
  • MFA enforced Yes
Router Store and Millbeck customers: IoT router customers qualify for a free 12-month Pro trial. Enter your order number at registration to unlock it. No card required during the trial period.
Security

Secure by design. Not by checkbox.

Over 90% of cyberattacks are delivered by email. IoT devices are an underprotected new surface for that threat. IoTMail builds security into the platform so you do not have to configure it yourself.

Auth

Per-device SMTP credentials

Every device gets a unique system-generated username and password. One compromised device cannot be used to send as any other. Revoke a single device credential from the portal instantly without touching the rest of the fleet.

Enforcement

From: header binding

The authenticated SMTP username must exactly match the From: address on every message. A device authenticated as acme+gw-001 cannot send as acme+gw-002 or support@iotmail.co.uk. Enforced in the mail filter pipeline on every connection.

Transport

Mandatory TLS - no plaintext

Port 25 plaintext is not accepted under any circumstances. All connections require TLS 1.2 as a minimum. This is not opportunistic - it is enforced. Devices that cannot support TLS cannot use IoTMail, which is the correct outcome.

Domain auth

SPF, DKIM and DMARC

SPF authorises only Amazon SES to send from iotmail.co.uk. Every message is DKIM-signed. DMARC policy is reject - emails that fail alignment are rejected outright by receiving servers, not delivered to spam.

Abuse

Rate limiting and recipient diversity

Per-device send limits and recipient diversity limits are enforced per 24-hour rolling window. A Starter device can send to a maximum of 5 distinct addresses per day. Legitimate IoT devices alert a fixed small set - this limit is invisible to normal use and breaks spam economics entirely.

Monitoring

Bounce rate and anomaly detection

Bounce and complaint rates are tracked per account. Thresholds matching Amazon SES limits trigger warnings and automatic suspension. Volume anomaly detection alerts on sudden spikes consistent with a compromised device being used as a spam relay.

Fail-closed milter IP allowlisting (Pro+) MFA available all tiers MFA enforced on Enterprise Full audit log 512KB message size limit Executable attachment blocking No email body stored GDPR compliant Port 25 blocked
Device support

Works with any device that supports SMTP AUTH

If the device has an SMTP client and supports AUTH PLAIN or LOGIN over TLS, it works with IoTMail. Configuration is the same on every device: host, port, username, password. No OAuth, no browser flows, no proprietary SDKs.

Teltonika
RUT240, RUT241, RUT950, RUT956, RUTX09, RUTX11, RUTX12, TRB140, TRB142 and all RMS-managed devices
Milesight
UR32, UR35, UR41, UG65, UG67 gateways. AM307, EM500, VS330 sensors with gateway relay
Sierra Wireless
RV55, RV50X, MP70 and AirLink series with ALEOS firmware SMTP support
Robustel
R2000, R3000, R5020 series with standard SMTP event notification
Raspberry Pi / Linux
Any device running msmtp, sendmail, or a Python smtplib script. Custom firmware with SMTP library support.
Industrial controllers
Any PLC, SCADA system, or industrial controller with SMTP alert capability and TLS support
Configuration for any device: SMTP server: smtp.iotmail.co.uk. Port: 587 (STARTTLS) or 465 (SMTPS). Username: your-handle+device-tag (example: acme+gw-001). Password: as shown in the portal. From address: username@iotmail.co.uk (must match username exactly).
Why IoTMail

What makes a dedicated IoT SMTP service different

Generic SMTP services are built for humans sending newsletters, transactional emails and marketing campaigns. IoT devices send differently. They send at odd hours, in bursts, from fixed IP addresses, to a small fixed set of recipients, with repetitive content. That pattern looks like abuse to a generic service.

IoTMail is built with M2M sending patterns as the normal case. Per-device accountability means one noisy device does not affect the rest of your fleet. The sub-addressing model means recipients can filter and route by device without any changes to their mail infrastructure.

The relay backbone is Amazon SES - the same infrastructure used by the largest senders on the internet. IoTMail handles the authentication, enforcement, and abuse controls. SES handles deliverability, reputation management, and inbox placement.

IoTMail vs generic SMTP
Feature IoTMail Generic
Per-device credentials Yes No
M2M patterns not flagged Yes No
From: header enforcement Yes No
Instant credential revocation Yes No
Device silence detection Yes No
UK-based, GDPR compliant Yes Varies
Frequently asked questions

Common questions

What is IoTMail and what does it do?
IoTMail is a dedicated SMTP relay service for IoT devices, sensors, routers, gateways and M2M equipment. Devices connect using standard SMTP with per-device credentials and IoTMail relays outbound email through Amazon SES. The platform handles authentication, TLS enforcement, From: header validation, rate limiting, abuse prevention and delivery logging. It is purpose-built for machine-to-machine sending patterns, not human email workflows.
Why can't I use Gmail, Outlook or a generic SMTP service for IoT devices?
Generic SMTP services treat machine-volume senders as potential abuse. IoT devices send repetitive content at odd hours from fixed IPs to small fixed recipient lists - that pattern triggers spam filters and account suspension on consumer email platforms. Consumer ISPs also block outbound port 25 entirely. IoTMail is built with M2M sending as the intended use case, not an edge case to be tolerated.
What SMTP ports and authentication methods does IoTMail support?
IoTMail accepts connections on port 587 with STARTTLS and port 465 with implicit TLS (SMTPS). TLS 1.2 is the minimum accepted version. Authentication uses SMTP AUTH PLAIN and LOGIN. Port 25 plaintext is not accepted under any circumstances - this is a hard requirement, not an option.
How do per-device credentials work?
When you add a device in the portal, IoTMail generates a unique SMTP username and password for that device. The username takes the format handle+devicetag - for example acme+gw-001. The password is a long randomly generated string. These credentials authenticate only that specific device and cannot be used to send as any other device. If a device is compromised, revoke its credential from the portal and generate new ones - no other devices are affected.
Does IoTMail work with Teltonika routers?
Yes. Teltonika RUT and RUTX series routers support SMTP email alerts natively in the firmware. Configure the SMTP server as smtp.iotmail.co.uk, port 587, STARTTLS enabled, with the username and password from your IoTMail portal. The device tag in the username makes it straightforward to identify which device sent each alert in your inbox.
What is the free router customer trial?
Customers who have purchased IoT routers from the Router Store or Millbeck qualify for a free 12-month Pro tier trial. Enter your order number during registration to unlock it. No payment card is required during the trial. At the end of the 12 months the account drops to Starter unless you subscribe to Pro.
Is IoTMail GDPR compliant?
Yes. IoTMail is UK-domiciled. No email body content is stored on IoTMail infrastructure - logs contain metadata only: sender address, recipient count, timestamp, message ID and delivery status. Account deletion triggers full data purge within the defined retention window. Data Processing Agreements are available for Enterprise customers on request.
What happens when a device goes silent?
IoTMail includes silence detection. Devices that have not sent for a configurable period are flagged in the portal dashboard and can trigger a notification. This catches the operationally dangerous scenario where an alert chain has silently broken - one of the most common and invisible failure modes in IoT deployments, where the absence of alerts is misread as everything working correctly.
Get started today

Your devices should send. Your alerts should arrive.

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