At a glance. Examples: Receipts, resets, codes, alerts · Trigger: One person's action · Keep apart: Separate from marketing · Note: Not legal advice
The short version
- A plain definition. A transactional email is an automatic message triggered by a person's action or an account event, and sent to that person alone.
- How it differs from marketing email. Marketing email is sent to many people to promote something, usually on a schedule that you choose.
- What counts and what does not. A receipt is transactional.
- What transactional email needs to do. It has to arrive quickly, because someone is waiting on the other end of a password reset.
- Authenticate your domain. Mailbox providers decide quickly whether to trust a message.
- Keep transactional and marketing apart. Send the two from separate streams, ideally on different subdomains such as mail.yourdomain.com and news.yourdomain.com.
A plain definition
A transactional email is an automatic message triggered by a person's action or an account event, and sent to that person alone. Typical examples are a purchase receipt, a password reset link, a sign-up confirmation, a one-time passcode, a shipping notification and a security alert.
The person is expecting it. That expectation is why these messages are opened far more often than promotions, and why delivery speed matters so much.
How it differs from marketing email
Marketing email is sent to many people to promote something, usually on a schedule that you choose. Transactional email is sent one at a time, as events happen. The first needs permission to market to the person. The second is part of the service they asked for.
The two behave differently in the inbox, too. Recipients complain about marketing more often, so mailbox providers watch it more closely. Mixing them lets a complaint about a promotion hurt the delivery of a password reset.
What counts and what does not
A receipt is transactional. A receipt with a large promotional banner is a grey area, and rules in some countries look at the main purpose of the message. A newsletter, a sale announcement and a product launch email are marketing, even if you send them from the same system.
If you are unsure, ask whether the person would be annoyed not to get it. If the answer is yes, it is probably transactional. This is general information, not legal advice, so check the rules where your recipients live.
What transactional email needs to do
It has to arrive quickly, because someone is waiting on the other end of a password reset. It has to arrive reliably, because a missing receipt becomes a support ticket. And it has to be clear, with a recognisable sender name and one obvious action.
Keep it short and plain. Put the key information, such as the code or the link, near the top, and say what to do if the person did not request it.
Authenticate your domain
Mailbox providers decide quickly whether to trust a message. Publish SPF and DKIM for your sending domain and add a DMARC record, so receivers can see the mail really comes from you. This matters most for transactional mail, where a message sent to spam is a failed product experience.
Use a domain you control in the From address, and keep a consistent sender name so recipients recognise it.
Keep transactional and marketing apart
Send the two from separate streams, ideally on different subdomains such as mail.yourdomain.com and news.yourdomain.com. That way each builds its own reputation, and a spike in marketing complaints does not slow down your receipts.
Some sending services also give you separate keys or settings per stream. Whichever way you do it, keep the rule simple and consistent.
Handle bounces and unsubscribes sensibly
Remove addresses that hard bounce so you do not keep sending to them. Respect a person's request to stop marketing mail, but understand that account and security messages are different: a person closing their marketing subscription does not turn off their password reset.
Log every send and every delivery event. When a customer says they never got the email, your logs are how you answer.
SMTP or API?
You can send transactional mail through an SMTP relay or through an API. SMTP is the quickest if your software already supports it. An API gives you finer control, such as templates with variables, and clearer responses.
Many teams use both, one for off-the-shelf software and one for their own code. Our guide to SMTP relays shows how to connect each.
Choosing a provider
Compare on your real monthly volume, delivery speed and reporting, log retention, and support. Check whether they offer a free plan for testing, whether they support both SMTP and an API, and whether billing suits you.
If you invoice in rupees or euros, check whether the provider bills in your currency and issues proper invoices. Our pricing page lists plans by volume, and our migration guides help if you are leaving another provider.
A short checklist
Before you launch, check that each message has a clear sender name and subject, that a recipient can tell what to do, that your domain has SPF, DKIM and DMARC, and that you can see delivery status for any message you sent.
Then test the unhappy paths. Request a password reset for an address that does not exist, send to a full mailbox, and see what your system does with the bounce. Those cases are what you will be debugging in production otherwise.
Further reading and sources
Related guides and tools
- SMTP relay explained: How relaying works and how to set one up.
- DKIM, SPF and DMARC setup: Authenticate your domain end to end.
- Bounce code lookup: Decode SMTP and enhanced status codes.
Ready to try it? Start on the free plan and send your first message in minutes.
Frequently asked questions
What is a transactional email?
An automatic email triggered by a person's action or an account event and sent to that person, such as a receipt, a password reset or a shipping update.
What is the difference between transactional and marketing email?
Marketing email promotes something to many people. Transactional email is one-to-one and tied to an action. Different rules and different reputation concerns apply, so keep them on separate streams.
Should I send transactional email through SMTP or an API?
Either works. SMTP is quickest if your software supports it. An API gives more control, such as templates and event data.
Can I put promotions in a transactional email?
It is a grey area, and some countries look at the main purpose of the message. Keep transactional mail focused on the event, and check the rules where you send. This is not legal advice.