An SMTP relay service takes the mail your application or mail server produces and delivers it to the recipients' mailboxes, from IP addresses that mailbox providers trust. Plenty of services do that. They differ in the places you only notice later: whose servers carry the mail, whose reputation your messages share, who acts when delivery breaks, and where your data sits. Here are the questions we would ask, each with Teneo's own answer under it so you can compare.
1. Whose servers and IP addresses does the mail leave from?
Ask who runs the mail transfer agents and who owns the IP range. It decides who can fix a delivery problem. If you want the background, we explain what such a server does in our guide to the mail transfer agent.
At Teneo: Teneo BV is a Belgian company in Oostkamp and has run SMTP relay infrastructure since 2007. The relay runs on AWS in Ireland (EU), on Teneo's own IP range. The people who run the servers are the people who answer your ticket.
2. Do you get dedicated IP addresses, and when?
On a shared IP address, other senders' behaviour counts against you. A dedicated address is yours alone, but a new one has no history, and mailbox providers want to see volume arrive in steps. Ask how a provider handles that.
At Teneo: every client gets dedicated IP addresses. A new account starts in the shared pool. When the delivery data shows that your flow needs its own address, we assign one. The console then raises the volume on the new IP in steps, using your own mail, and only on days with enough volume to count. It runs by itself; there is nothing for you to order or manage.
3. Who looks after reputation?
An address that lands on a blocklist stops delivering. Ask who checks, how often, and who acts.
At Teneo: the console checks every IP against all the blocklists that matter, every hour, and reads Microsoft SNDS and Google Postmaster data. It rotates DKIM keys on request and checks your SPF and DKIM records every hour. Feedback loops are handled for you. Our guide on rotating a DKIM key shows how that part works.
4. What happens when something goes wrong?
Two parts matter here: can you see what happened, and does a person act or a rule?
At Teneo: the delivery log shows every message with the receiving server's own answer in plain words, kept for 12 months. A ticket in the console reaches the engineers who run the platform. We never suspend an account automatically. If something looks wrong on your account, a person looks first.
5. Where does your data go, and how long does it stay?
You send invoices, payslips and login codes through this service, so the answer is a compliance question as well as a technical one.
At Teneo: the servers, queues and logs are in Ireland, inside the EU. Message bodies are not kept after delivery. A message waits in the queue until it is delivered, at most 48 hours, then it is dropped and reported to you as a bounce. Delivery logs hold metadata only (sender, recipient, subject line, times, result), for 12 months. We sign a data processing agreement under article 28 GDPR in English, Dutch or French, and list our sub-processors on the privacy page. We are not ISO-certified.
6. How do you connect?
Business software wants SMTP settings. Code you write may prefer an API. Check that both exist, and that they lead to the same place.
At Teneo: SMTP on tlsrelay.teneo.be, port 587 with STARTTLS, one relay login per mail stream. There is also an HTTPS Submission API for single messages or batches of 500, with an idempotence key. Both use the same IP addresses and the same delivery log. Setup takes under five minutes: create an account, publish two DNS records (SPF and DKIM), and change one setting. Our guide on SMTP relay or email API helps you pick.
7. What does it cost, and what is on the invoice?
Ask for the price at your volume, whether there is a setup fee, and whether you pay for what you send or for what you reserved.
At Teneo: the plan at no charge allows 100 messages a day, for as long as you like. Above that there is one monthly price set by your volume, from € 134.75 excl. VAT for 100,000 messages a month. There is no setup fee, and the invoice follows what you sent. Above five million a month we talk.
8. What mail does the service accept?
This one protects you. A service that takes any sender fills its IP addresses with the wrong kind of mail, and you share the result.
At Teneo: consent-based mail only, at any volume. No cold email and no bought lists. The rules are in our acceptable use policy.
9. Can you reach a person before you buy?
At Teneo: you do not need a sales call to start. Create an account and send a test message. If you want to talk before that, write to us; we answer within one working day.
Who this suits
Teneo suits companies whose mail has to arrive: invoices, login codes, order updates, payslips, and campaigns sent to people who asked for them. It suits software teams that want an SMTP or API door and engineers who answer. It does not suit cold outreach, and it is more than you need for a few hundred mails a month from an office mailbox.
Frequently asked questions
What is an SMTP relay service?
An SMTP relay service accepts e-mail from your application or mail server over SMTP, or over an HTTPS API, and delivers it to the recipients' mail servers from IP addresses with an established reputation. You hand over the message and the relay handles queueing, retries, authentication and delivery.
How is an SMTP relay different from my own mail server?
Your mail server sends from your IP address, and you keep its reputation, reverse DNS, blocklist checks and queue in order. A relay does that for you. You can keep your mail server and set the relay as its smart host, so outbound mail leaves through the relay.
Do I need dedicated IP addresses?
For mail that has to arrive, dedicated addresses are the safer choice, because no other sender can affect their reputation. At Teneo every client gets them; a new account starts in the shared pool and moves to its own IP address once the delivery data shows that the flow needs one.
Is an SMTP relay service the same as an email API?
They are two ways to reach the same service. SMTP suits existing software and mail servers, an API suits code you write yourself. At Teneo both lead to the same IP addresses and the same delivery log.
Where does Teneo process my mail?
On AWS in Ireland, inside the EU, on Teneo's own IP range. Teneo BV is a Belgian company. Message bodies are not kept after delivery and delivery logs are kept for 12 months.