What is an SMTP relay and how does it work

One reliable sending point for all your applications.

An SMTP relay is an outgoing mail server through which your software sends email, instead of sending directly from your own webshop, server or application. That gives you central control, authentication and delivery — without every system needing its own mail configuration, reputation and IP address.

relay.2mail.eu port 587 TLS Belgian servers
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The basics

What is an SMTP relay?

An intermediate station that expertly forwards every outgoing email from your applications to your recipient's inbox.

SMTP (Simple Mail Transfer Protocol) is the standard protocol servers and applications use to send email. When a webshop, CRM, ERP package or your own server sends directly, it usually does so from an IP address without any sending history. Mailbox providers such as Gmail, Outlook and Proximus do not know that address, do not trust it, and often filter messages out automatically — straight into the spam folder or, worse, with a hard rejection.

An SMTP relay solves this by positioning itself between your application and the final recipient. Instead of every application managing its own mail server, IP reputation and the right authentication records, everything is sent through a single controlled, warmed-up and authenticated sending point. That relay monitors the quality of each outgoing message, applies rate limits where needed, and makes sure mailbox providers recognize and trust the sender.

Why central sending makes the difference

The result is one place to configure authentication, one place to follow up delivery, bounces and rejections, and one party responsible for the reputation of the sending IP address. For a company that mails from several systems — a webshop for order confirmations, a CRM for customer communication, a server for notifications — that is the difference between loose, vulnerable sending channels and one professionally managed mail infrastructure.

When do you need an SMTP relay?

As soon as something other than a human sends email. These five situations are how you tell.

  • Your webshop sends order confirmations, and customers phone to ask whether their order went through.
  • Your application sends password resets, and users report that the mail "never arrives".
  • Your invoicing package sends invoices that land in spam with some customers.
  • The form on your website works to your own mailbox, but not for customers with an address at a large provider.
  • You send from several systems and nobody knows any more which server sends what.

If you recognize any of these situations, the problem is rarely the content of your messages. It is the route they take.

What a relay does not solve

A bad list or a bad message. A relay delivers, but whether anyone opens it is up to you. A relay also does not put an end to a forgeable domain: you still need to add the relay to your SPF record and enable DKIM for your domain. Skip that and you have moved the problem rather than solved it.

The route of a message

From your application to the inbox

Three steps, one controlled path. This is how every email travels through the 2mail relay.

Step 1 · Sender

Your application

Webshop, CRM, ERP or server hands the email over via SMTP using your own credentials.

Step 2 · 2mail relay

2mail relay

Authentication, rate limiting, automatic retry and logging on Belgian infrastructure.

Step 3 · Recipient

The inbox

The message arrives recognized and trusted at Gmail, Outlook, Proximus and the like.

Your domain remains the sender — the relay sends on your behalf, not on behalf of 2mail.

2mail — smtp-config
hostrelay.2mail.eu
port587 // submission
encryptionTLS (STARTTLS)
usernameyour 2mail login
passwordyour 2mail password
Connection verified & encrypted
The settings

Five fields, and you send via 2mail

You connect every application with exactly the same SMTP details. Enter them once in your webshop, CRM, ERP or mail application and all outgoing mail from that system runs through our infrastructure from then on — without any further changes to your software.

  • Port 587 with TLS is the universally supported standard for authenticated sending.
  • Your personal login authenticates every message — no open or anonymous sending route.
  • You connect multiple applications through the same or separate logins, each with its own insight.
In practice

How to connect your application

From SMTP details to fully live traffic, in four clear steps.

Enter the SMTP details

Add the host, port 587 and your personal login in your application. Done in a few minutes.

Set up authentication

The dashboard creates your DKIM key and the DNS records for SPF, DKIM & DMARC in one click. You publish them with your DNS provider and then check them in one click.

Testing & building up volume

You test the connection with a first message and see the result per message in the dashboard. After that you build up the volume gradually yourself.

Live with monitoring

You send live while we continuously monitor delivery, bounces and rejections.

Why not send directly

Managed relay or direct sending?

Sending directly from a webshop, server or application looks simple, but in practice brings a series of risks. A single misconfigured application can undermine the deliverability of all your email — including critical system messages.

Direct sending

Every system on its own
  • IP address without sending history or reputation
  • SPF, DKIM & DMARC configured manually and often incorrectly
  • No protection against sudden volume spikes
  • No automatic retry on greylisting or throttling
  • No central view of bounces and rejections
  • High risk of the spam folder or a hard rejection
vs

Via the 2mail relay

One managed sending point
  • Warmed-up, randomized IP pool on Belgian servers
  • SPF, DKIM & DMARC: records ready, checked in one click
  • Rate limiting per domain protects your reputation
  • Automatic retry on temporary errors
  • Full logging of every rejection and bounce
  • High deliverability and personal follow-up

With 2mail you do not have to manage a mail server, build up an IP reputation or interpret bounce and rejection reports by hand: we do that, with personal support whenever you need it. Everything runs in line with Belgian and European data protection rules (GDPR), on infrastructure that JAAN bv has managed from Zelzate since 2000.

What you use it for

Typical uses of an SMTP relay

WebshopOrder confirmations and shipping notifications that always arrive.
CRMCustomer communication and automatic follow-up from your system.
Your own serverSystem and error messages from your applications and scripts.
Accounting softwareInvoices and payment reminders that are delivered reliably.

Would you like to dive deeper into deliverability, or specifically into transactional email such as order confirmations and password resets? Then read more about email deliverability or about transactional email at 2mail.

Sending campaigns over the same relay as well? Then have a look at email marketing at 2mail, the steps for sending a mailing, and what that costs under our pricing.

Connect your own system

Automate with the API and webhooks

Besides SMTP, 2mail can be driven over HTTPS. Useful when you would rather work with JSON than a mail configuration, or when you want to decide per message when it goes out and whether opens are tracked.

Send through the APIA single call with sender, recipient and content. You get an id back straight away to look up the status later.
WebhooksWe push every event to your own URL as soon as we know about it — delivered, bounced, opened. Signed, with automatic retries.
A key per applicationEach application gets its own key that may only send, and that you can revoke on its own without touching the others.

What you can build with it, with examples, is on the email API page. The full reference with every field is in the interactive API documentation.

Further reading

Port 25 blocked? Recognise it and solve it via port 587
SMTP relay Belgium Belgian servers, for the Belgian market
European SMTP relay (GDPR) Processing and logs inside the EU, for IT

Frequently asked questions about SMTP relay

An SMTP relay is a sending server your applications use instead of sending mail themselves. Your web shop, CRM or accounting package hands the message to the relay with a login, and the relay takes care of delivery: authentication, reputation, retries on temporary errors and reporting per message.
As soon as something other than a human sends email: a web shop with order confirmations, an application with password resets, an accounting package with invoices. Technically a web server can send mail, but it has no reputation, is not in your SPF record and signs nothing with DKIM — to the receiver that looks like spam.
No. A mail server also receives and stores mail for your users. A relay only sends. Your mailboxes stay where they are, for example at Microsoft 365; only your applications move to the relay.
For a handful of messages a day, often yes. Mailbox providers usually impose low daily limits and are not built for automated mail. As soon as a web shop or application sends hundreds of messages a day, you run into those limits.
Port 587 with STARTTLS is the standard for authenticated sending and is supported by almost every package. Port 25 is meant for traffic between mail servers and is blocked for outgoing traffic by many providers and cloud hosts.
With anything that speaks SMTP, and that is almost every package: WordPress, WooCommerce, Odoo, PrestaShop, Magento, Laravel, Microsoft 365 and any ordinary mail client. You enter a server name, a port and credentials in the SMTP settings.
SMTP is the fastest route: almost every system has a settings field for it. A REST API is more convenient when you build software yourself and want a status back per message: you send with an API key and webhooks report what happened to each message. At 2Mail both routes exist side by side.
Yes. You add the relay to the SPF record of your domain and enable DKIM, so the receiving server can establish that the relay is allowed to send on your behalf. At 2Mail you are given the right records and we help you set them up.

Connect your first application

We help you personally with the configuration and IP warm-up, on Belgian infrastructure and in line with the GDPR.

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