Professional SMTP relay

A professional SMTP relay is an external sending server that takes the emails produced by your websites, copiers and business software and hands them over to the recipients’ mail servers. A professional SMTP relay replaces the sending server of your hosting provider or of Microsoft 365 when that server throttles, blocks or sends your messages to spam. Service-smtp.eu is a professional SMTP relay operated in France since 2009, with French IP addresses, SPF and DKIM on your domain, and a quota stated up front from €29 a year excl. VAT.

You are here with a specific problem, and it is not the same one for everybody. The website whose order emails no longer arrive. The copier that refuses to send its scans since the mailboxes moved to Microsoft 365. The property management or accounting software that sends receipts and reminders and hits a sending limit. Or simply the office mail client that has to work from a hotel, a trade show or a customer’s network. All four situations are solved with the same relay. The account is created online, the subscription is active within five minutes of payment, and you plug in right away.

What exactly is a professional SMTP relay?

An SMTP relay is an intermediate server: your software, website or device hands it a message, the relay authenticates it, then passes it on to the recipient’s mail server. If you already know all this, skip straight to the limits or to the setup. For everyone else, it works in three steps.

Step	What happens	What you see
Sending	Your application connects to the relay on an allowed port, with a username and a password	The message leaves your software
Checking	The relay verifies your credentials, signs the message with DKIM and presents it from an IP address declared in your SPF record	Nothing, and that is the point
Delivery	The relay hands the message to the recipient’s server and records the answer: delivered, deferred or rejected (the “bounce”)	The status in your sending history

What separates a professional relay from a plain sending server happens at the second step. The SMTP server that comes with shared hosting just sends. Nobody there watches the reputation of the IP addresses, nobody hands you a DKIM record to publish, and nobody tells you whether the message got accepted at the far end. A professional relay does those three things, and that is what you pay for.

Why the SMTP server of your host or of Microsoft 365 is no longer enough

The sending server included with your hosting plan or your office suite was designed for human email. One person, one mailbox, a few dozen messages a day. A website, a copier or a line-of-business application does not behave like a person, and the ceilings come fast.

Limits recorded on 2 September 2026 from the official documentation, to be checked again before sizing a project:

Sending server	Documented limit	What it means in practice
OVHcloud web hosting	Starter 20 an hour, Personal 100, Pro 200, Performance 2,000, and only for PHP’s mail() function. Past the quota, messages sit in a queue	A shop sending a confirmation, an invoice and a shipping notice fills a Personal plan after 33 orders in the same hour
IONOS Mail Basic or Mail Business	50 emails an hour during the first week, 500 after 30 days. Above that, error 450 Mail send limit exceeded	An end-of-month invoice reminder run is stopped dead
Microsoft 365, SMTP AUTH client submission	10,000 recipients a day and 30 messages a minute per mailbox. TLS 1.2 or later required, SMTP AUTH disabled by default for organisations created after January 2020	An older copier that cannot speak TLS 1.2 can no longer send at all, whatever the volume
Google Workspace, Gmail	2,000 messages a day per user, 3,000 external recipients a day. A user who goes over is blocked for 24 hours	Business software sending through an employee’s account locks that employee out of their own mailbox

Volume is not the only problem, either. On shared hosting, your website shares its sending IP address with hundreds of others. It takes one hacked neighbour for the IP to land on a blocklist, and your order emails land there with it. Not your fault, and nothing you can fix from your side. Microsoft says as much in its own documentation: Exchange Online is not designed for application sending in volume, and points you to a relay instead.

That is exactly what an external relay is for. It has its own IP addresses, its own reputation, and it is not tied to a mailbox.

What a professional relay does that a free one does not

Free relays exist, and it would be dishonest not to mention them. The Google Workspace relay service, Brevo’s free tier, or the host’s own SMTP server. They do the job in some cases, and not in others.

Criterion	Host’s SMTP server	Google Workspace relay	Brevo, free tier	Service-smtp.eu
Quota	An hourly rate, 20 to 200 an hour at OVHcloud depending on the plan, up to 4,800 a day on Pro if sending is spread out, but for the PHP mail() function only	10,000 a day per Workspace user	300 a day, Brevo logo in your emails	A daily ceiling, 100 to 10,000 a day depending on the plan, no branding
Prerequisites	None	A Google Workspace subscription, a fixed IP or per-account authentication	A marketing account, domain validation	An account, a login, a password
Sending IP	Shared with every customer of the host	Google	Shared with all free senders	French, monitored, dedicated IP as an option
SPF and DKIM on your domain	Rarely	Yes	Yes	Yes, provided
Status of each message	No	Admin logs	Marketing dashboard	Per-message history: delivered, deferred, rejected
Works with older copiers and software without TLS 1.2	Varies	No	Varies	Yes, plain or TLS mode, your choice
Bulk marketing sending	No	No	Yes, that is their business	No, strict anti-spam policy
Support	Hosting ticket	Google support	Community	By email, from the technicians who run the service

The last line matters as much as the others. Service-smtp.eu is not an emailing tool and does not try to be one: double opt-in newsletters and transactional messages are welcome, mass prospecting is not. If what you need is to send 50,000 promotional messages on the same morning, an emailing platform with a dedicated IP will do better, and we will tell you so.

The criteria that matter when choosing an SMTP relay

When you compare private or professional SMTP relay offers, every sales page lines up the same words. Here is what actually makes a difference in the field, and where service-smtp.eu stands on each point.

French IP addresses with a monitored reputation. Our servers are hosted in France and use French IPs only. Their reputation has been our trade since 2009: we automatically query the anti-spam blocklists to know whether a complaint targets one of our accounts, agreements with some Internet providers send complaints straight to us, and an account that generates them is suspended, because the IP it damages is yours too. Your messages never transit through servers outside Europe.

SPF and DKIM provided, with the guides. You publish two DNS records on your domain, and every message leaves authenticated and signed. The SPF setup guide and the DKIM guide are written step by step, with screenshots.

Ports that get through anywhere. Port 587 with TLS first, then 25, 465 with SSL, and a series of alternative ports for networks that block everything else. The unencrypted plain mode remains available for older copiers, which Microsoft 365 no longer accepts.

A status for every message. Each sending shows up in the history of your customer area with the recipient server’s answer. Delivered, deferred or bounced, you know without opening a ticket.

A written GDPR framework. A data processing agreement under Article 28 is available, signed by Spirion, the company that operates the service. Useful the day a customer or a DPO asks for your list of processors.

A readable quota, stated with the price. No per-message pricing, no overage billing. You choose a daily ceiling, you are warned at 80%, and you change plans when the need grows.

Limits, too. The service does no bulk marketing. The Personal, Team and Pro plans open immediately; the Business plans and the large credit packs are reserved for verified accounts, a free request from the customer area, handled by support, that protects the reputation of the IPs you share. And an account suspended for complaints will not be refunded. It is written in the anti-spam policy, better to know it beforehand.

What it costs, with the quota next to it

A price without a volume means nothing. Here are the annual plans, excluding VAT, with the daily ceiling that goes with them. Each plan has two thresholds, a number of emails and a transferred volume: whichever is reached first applies, and the counters reset every night at midnight, French time.

Plan	Emails a day	Volume a day	That is, in 5 MB scans	Who it is for	Annual price excl. VAT
Personal	100	50 MB	10 a day	A freelancer, a small site, a mail client on the road	€29
Team	500	100 MB	20 a day	An SMB, a shop, business software, a lightly used copier	€44
Pro	1,000	300 MB	60 a day	A busy online shop, a copier scanning all day long	€99
Business	2,500 to 10,000	1 to 4 GB	200 to 800 a day	A fleet of devices, an ERP, several websites	€240 to €960

Volume counts as much as the number for a copier: a 5 MB scanned bundle uses 5 MB of the ceiling. For a device that scans a lot, size on volume rather than on the number of sends, and take the next plan up during peak periods.

At this price, what is limited is the volume, nothing else. Above the ceiling, the account is suspended until midnight and you are notified by email; pending messages go out afterwards. A hosting provider does the same; the difference is that the ceiling is yours, that you are warned at 80%, and that you change plans online without waiting. The account is free to create and is paid at order time, with no commitment and no automatic renewal. The dedicated IP is an option at €240 excl. VAT a year, available from the Team plan. The details of each plan, pay-per-email credits and options are on the plans and options page.

One caveat on the five minutes: the Business plans first go through an account verification, done by support. For an immediate need, start on a Team or a Pro, which are active right away, and move to Business once the account is verified.

Do you install copiers or websites on behalf of your customers? A single customer account can hold several subscriptions, one per end customer, each with its own credentials, quota and invoice. There is no partner programme and no reseller price: there is the listed price, and one place to manage everything.

Set up your relay in ten minutes

Your subscription goes live within five minutes of payment; a confirmation email lets you know. From there, the customer area shows you three things: a host name, a username, a password. These are the only settings to copy into your software, your website or your copier, under labels that vary from one vendor to the next.

Setting	Value
Outgoing server, or SMTP host	The host shown in your customer area
Port	587 with TLS, recommended. Otherwise 25, 465 with SSL, or one of the alternative ports
Authentication	Yes, the account’s username and password
Encryption	TLS or STARTTLS preferably, SSL on 465, plain mode for older devices
Sender address	One on your own domain, once SPF and DKIM are published. The number of sender addresses is unlimited

A word on older devices. If the copier cannot do TLS 1.2, which rules it out at Microsoft 365, the relay accepts plain mode on the same ports. The message then travels unencrypted between the device and the relay. It is a trade-off to point out to the customer, and to keep for devices that have no other option.

Before touching the copier or the website, check that the port gets out of your network. The online SMTP test opens a real connection to the server and returns its answer, port by port, in ten seconds. The list of compatible servers and apps then gives the setup path for Exchange, Postfix, PrestaShop, WordPress and the most common CRM and ERP systems.

SMTP relay: the questions we get asked

What is an SMTP relay?

An SMTP relay is a server that receives the outgoing emails of an application, a website or a device, authenticates them, then passes them on to the recipients’ servers. It sits between your tool and the recipient’s mailbox. You use one when the sending server provided by your host or your office suite is limited, blocked or poorly rated.

Which outgoing SMTP server should a website or an application use?

For a person sending from a mailbox, the server of your email provider is enough. For application sending, a website, a copier, management software, you need a server that accepts login authentication, does not depend on a mailbox, and publishes SPF and DKIM on your domain. That is the definition of a professional SMTP relay.

Which SMTP settings need to be configured?

Five settings: the server host name, the port, authentication switched on, the username and password, and the encryption mode. With service-smtp.eu, port 587 with TLS is the recommended value; the other ports are fallbacks for when a network blocks it.

Is there a free SMTP relay?

Yes, and sometimes it is enough. The Google Workspace SMTP relay allows 10,000 messages a day per user, but it requires a Workspace subscription and a fixed IP or per-account authentication. Brevo’s free tier, and those of comparable emailing platforms, caps at 300 messages a day and adds its logo to your sends. Paying for a relay starts to make sense the day you need a quota you can count on, an IP somebody actually watches, and a history you can check message by message.

How do I set up an SMTP relay for Office 365?

Microsoft documents three routes: SMTP AUTH submission through a mailbox, relay via a connector tied to a fixed IP, or direct send, which only reaches internal recipients. Every one of them wants TLS 1.2, and the first is switched off by default on recent tenants. If your device cannot manage it, the page on scan to email not working with Office 365 details the causes and the workaround through an external relay.

Private SMTP relay and professional SMTP relay, what is the difference?

None in principle: both expressions describe a sending server reserved for identified customers, as opposed to a host’s shared SMTP server. “Private” stresses the isolation of reputation, “professional” the service framework, support and quota. At service-smtp.eu, full isolation exists as the dedicated IP option, from the Team plan.

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