Mailpit vs smtp4dev
A side-by-side comparison of two self-hosted mail servers options — licensing, setup difficulty, resource needs, and what each one replaces.
Mailpit
Email and SMTP testing tool with web UI
VS
smtp4dev
Fake SMTP server for development email testing
| Feature | Mailpit | smtp4dev |
|---|---|---|
| Deploy effort | Under-an-hour setup | Under-an-hour setup |
| Health score | 93 · Excellent | 85 · Excellent |
| Category | Mail Servers | Mail Servers |
| License | MIT | GPL-3.0 |
| Language | Go | C# |
| Setup difficulty | Easy | Easy |
| Min. RAM | 64 MB | 128 MB |
| Deployment | docker, binary | docker, binary |
| GitHub stars | ★ 10,426 | ★ 3,979 |
| First released | 2022 | 2015 |
| Replaces | Mailtrap, MailHog | Mailtrap |
What are Mailpit and smtp4dev?
Mailpit
Mailpit is a self-hosted email testing tool that acts as an SMTP server and captures all messages for inspection in a clean web interface. Developers use it to preview and debug application email locally.
- SMTP capture server
- Web message viewer
- REST API
- HTML and link checks
smtp4dev
smtp4dev is a dummy SMTP server that catches messages sent by applications and shows them in a web interface. It lets developers test email functionality without sending real mail.
- Catches outgoing email
- Web inbox viewer
- IMAP access
- API for automation
Mailpit vs smtp4dev: key differences
Mailpit is written in Go, while smtp4dev is built with C#. Licensing differs — MIT for Mailpit versus GPL-3.0 for smtp4dev. Mailpit is the lighter option, starting around 64 MB of RAM against 128 MB for smtp4dev. Smtp4dev is the more established project (first released 2015), while Mailpit arrived in 2022. Mailpit has the considerably larger community, at 10,426 GitHub stars versus 3,979.
Why pick each one
Choose Mailpit if…
- Very fast and small
- Great developer UX
Watch out for
- For testing not production
- Not a real mail server
Choose smtp4dev if…
- Easy local testing
- Cross-platform
Watch out for
- Not for real delivery
- Development use only
Frequently asked questions
Is Mailpit or smtp4dev better?
Neither is universally better. Mailpit has the larger community; both share a easy setup difficulty, so the decision comes down to features and licensing.
Are Mailpit and smtp4dev free and open-source?
Yes. Mailpit is licensed under MIT and smtp4dev under GPL-3.0. Both can be self-hosted at no software cost.
Can I run Mailpit and smtp4dev with Docker?
Mailpit: yes. smtp4dev: yes.
Which is lighter on resources, Mailpit or smtp4dev?
Mailpit has the smaller minimum footprint at 64 MB of RAM, compared to about 128 MB for smtp4dev. Real-world usage depends on library size, user count, and enabled features.