Start by deciding whether you need marketing campaigns and app email in one place or only reliable app email. Developer-first APIs suit products sending receipts and alerts; SMTP relays suit websites and plugins; combined platforms suit teams who want both. Then test setup, delivery monitoring and the API with one real message type before moving.
Elastic Email sells two products under one roof: an email marketing service and an email API, plus tools for team and customer communication. That's handy until you realise you only use one half. Most people searching for an alternative are developers or site owners who mainly need app email to arrive reliably: password resets, receipts, order confirmations and alerts. This list is built for them.
Split marketing mail from app mail
The first decision is whether to keep both kinds of email together. Marketing email is sent in batches to people who signed up; transactional email is triggered one by one by something a user did. They behave differently, they're judged differently by inbox providers, and many teams find it simpler to run them separately so a problem with one doesn't drag down the other.
Whichever way you go, the thing to test in any replacement is how sending is set up, how deliverability is monitored, and what the API gives your developers. Setup means domain verification and how quickly you can send a first message. Monitoring means seeing bounces, complaints and delays without digging. The API means clear documentation, sensible errors and webhooks for events such as opens and bounces. Tools here split by who they're built for and how much you set up yourself.
Don't forget the people who aren't developers. Someone in support will one day need to check whether a customer's password reset was delivered, so look at how easily you can search the message log by email address, and how long those logs are kept. A provider that only shows totals leaves your support team guessing.
Eight sending services compared
| Tool | Service type | Good for |
|---|---|---|
| MailerSend | Email API and SMTP | Team-friendly sending for modern apps |
| Mailgun | Transactional email API | Sending, receiving and tracking email from code |
| Mailjet | Marketing and transactional email | Marketing and app email from one platform |
| Mailtrap | Email delivery platform | Developer and product teams sending app email |
| Postmark | Transactional email service | Getting app email to the inbox on time |
| Resend | Developer email platform | Transactional and marketing email built for developers |
| SendLayer | SMTP relay and email API | Connecting website emails through a relay |
| SMTP2GO | Email delivery service | Worldwide servers with reporting on every send |
Grouped by how you send
API first, for developers
Resend, Mailgun and Postmark are built around an API that your code calls. All three focus on transactional email, and the first and last of those also mention marketing email.
API or SMTP, for product teams
MailerSend and Mailtrap offer both an API and SMTP, and both pitch themselves at developer and product teams working together.
SMTP relay, for websites
SendLayer and SMTP2GO suit website owners who need form and order emails from their site to arrive, usually by plugging relay details into a plugin or server setting.
Marketing and app email together
Mailjet keeps marketing and transactional email in one platform, the closest match if you liked having both under one login.
All eight, A to Z
In no particular order, listed alphabetically. Every line reflects how the vendor describes its own service.
MailerSend
Best for: Product teams wanting an email API or SMTP that the whole team can work with, with a free plan named on the vendor's site.
Mailgun
Best for: Developers who need APIs to send, receive and track transactional email, on a service the vendor says is built with developers in mind.
Mailjet
Best for: Marketers and developers sharing one tool for designing, sending and automating both marketing and transactional email, with GDPR compliance stated by the vendor.
Mailtrap
Best for: Developer and product teams sending app email through an API or SMTP, where the vendor highlights fast delivery and round-the-clock support.
Postmark
Best for: Developers who care most about transactional email arriving quickly, with marketing email also offered, as the vendor describes its service.
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Resend
Best for: Engineering teams sending transactional and marketing email at scale who want mail that reaches people rather than spam folders, per the vendor.
SendLayer
Best for: Website owners connecting their site's emails through an SMTP relay or API, so form and order emails get delivered, as the vendor pitches it.
SMTP2GO
Best for: Businesses wanting a sending service with servers around the world, an API and detailed reporting, plus a free plan the vendor mentions.
Advice before you switch sending providers
Move one message type at a time. Start with something low risk, like a welcome email, watch delivery for a few days, then move password resets and receipts. Switching everything in one go makes it hard to tell which change caused a problem if messages start landing in spam.
Keep your old account active until the new one has handled real traffic without trouble, and keep a copy of your templates outside either service. If you send from a website rather than an app, my guide to WordPress SMTP plugins shows how sending connects to your site, and my list of developer email APIs covers more options for app mail.
Domain and sending checklist
- Verify your sending domain with the new provider and add the authentication records it gives you, such as SPF and DKIM.
- Set up a DMARC record if you don't have one, starting with a monitoring policy.
- Use a subdomain for app email if your marketing email shares the main domain.
- Point bounce and complaint webhooks at your app so bad addresses stop being mailed.
- Send test messages to a few inbox providers and check they arrive in the main inbox.
- Switch traffic gradually and watch bounces and complaints daily for the first week.
Do you make transactional email software? Tool makers can ask to be considered for a featured place on this list.
Want your tool on this list? Featured spots and reviews here are paid partnerships. Here's how to partner with me.
Frequently asked questions
What is transactional email?
It's email triggered by something a user does, such as signing up, resetting a password or placing an order. It's sent one at a time, and people expect it to arrive straight away.
Should marketing and transactional email use the same service?
They can, but many teams separate them, or at least use different subdomains, so a problem with a marketing send doesn't affect receipts and password resets.
What's the difference between an email API and SMTP?
An API is called directly from your code and usually gives richer data back. SMTP is the standard sending protocol, so it works with almost any plugin, framework or server without extra code.
Will switching providers hurt my deliverability?
It can for a short while if you switch everything at once. Authenticate your domain fully, move traffic gradually and watch bounces and complaints closely.
Do I need consent to send transactional email?
Transactional messages tied to an action a user took are treated differently from marketing in many places, but rules vary by country. Check your regulator's guidance, especially before adding promotional content.
