smtp4dev vs swaks
A side-by-side comparison of two self-hosted mail servers options — licensing, setup difficulty, resource needs, and what each one replaces.
| Feature | smtp4dev | swaks |
|---|---|---|
| Deploy effort | Under-an-hour setup | Read-the-docs project |
| Health score | 85 · Excellent | 15 · At risk |
| Category | Mail Servers | Mail Servers |
| License | GPL-3.0 | GPL-2.0 |
| Language | C# | Perl |
| Setup difficulty | Easy | Easy |
| Min. RAM | 128 MB | 16 MB |
| Deployment | docker, binary | binary, source |
| GitHub stars | ★ 3,979 | ★ 1,344 |
| First released | 2015 | 2003 |
| Replaces | Mailtrap | Mailtrap |
What are smtp4dev and swaks?
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
swaks
swaks is a flexible command-line SMTP transaction tester used to diagnose and verify self-hosted mail servers. It can craft and send test messages with fine control over the SMTP conversation.
- Command-line SMTP tester
- Fine control over SMTP transactions
- Diagnoses mail server issues
smtp4dev vs swaks: key differences
Smtp4dev is written in C#, while swaks is built with Perl. Licensing differs — GPL-3.0 for smtp4dev versus GPL-2.0 for swaks. Swaks is the lighter option, starting around 16 MB of RAM against 128 MB for smtp4dev. Swaks is the more established project (first released 2003), while smtp4dev arrived in 2015. Smtp4dev has the considerably larger community, at 3,979 GitHub stars versus 1,344. Smtp4dev lists first-class Docker deployment; swaks does not.
Why pick each one
Choose smtp4dev if…
- Easy local testing
- Cross-platform
Watch out for
- Not for real delivery
- Development use only
Choose swaks if…
- Released under the GPL-2.0 license
- Easy to set up — beginner-friendly
- Active community (1.3k GitHub stars)
- Written in Perl
Frequently asked questions
Is smtp4dev or swaks better?
Neither is universally better. smtp4dev has the larger community; both share a easy setup difficulty, so the decision comes down to features and licensing.
Are smtp4dev and swaks free and open-source?
Yes. smtp4dev is licensed under GPL-3.0 and swaks under GPL-2.0. Both can be self-hosted at no software cost.
Can I run smtp4dev and swaks with Docker?
smtp4dev: yes. swaks: check the project docs for container support.
Which is lighter on resources, smtp4dev or swaks?
swaks has the smaller minimum footprint at 16 MB of RAM, compared to about 128 MB for smtp4dev. Real-world usage depends on library size, user count, and enabled features.