Exim vs WildDuck
A side-by-side comparison of two self-hosted mail servers options — licensing, setup difficulty, resource needs, and what each one replaces.
| Feature | Exim | WildDuck |
|---|---|---|
| Deploy effort | Read-the-docs project | Under-an-hour setup |
| Health score | 15 · At risk | 86 · Excellent |
| Status | Archived | Actively maintained |
| Category | Mail Servers | Mail Servers |
| License | GPL-2.0 | EUPL-1.2 |
| Language | C | JavaScript |
| Setup difficulty | Hard | Hard |
| Min. RAM | 64 MB | 1,024 MB |
| Deployment | bare-metal, source | docker, bare-metal |
| GitHub stars | ★ 785 | ★ 2,108 |
| First released | 1995 | 2017 |
| Replaces | Microsoft Exchange | Microsoft Exchange, Gmail |
What are Exim and WildDuck?
Exim
Exim is a highly configurable mail transfer agent used to route and deliver email on Unix systems. It powers a large share of the internet's mail servers and supports extensive policy and ACL controls.
- Powerful routing rules
- ACL-based policy
- Wide platform support
- Mature codebase
WildDuck
WildDuck is a modern, scalable mail server providing IMAP, POP3, and a full REST API for managing mailboxes. It stores messages in MongoDB and is designed for clustered, highly available deployments.
- IMAP and POP3
- Full REST API
- MongoDB storage
- Designed for scale
Exim vs WildDuck: key differences
The biggest difference is maintenance: Exim's repository is archived and no longer developed, while WildDuck is actively maintained. Exim is written in C, while WildDuck is built with JavaScript. Licensing differs — GPL-2.0 for Exim versus EUPL-1.2 for WildDuck. Exim is the lighter option, starting around 64 MB of RAM against 1,024 MB for WildDuck. Exim is the more established project (first released 1995), while WildDuck arrived in 2017. WildDuck has the considerably larger community, at 2,108 GitHub stars versus 785. WildDuck lists first-class Docker deployment; Exim does not.
Why pick each one
Choose Exim if…
- Extremely flexible
- Proven at scale
Watch out for
- Complex configuration
- Easy to misconfigure
Choose WildDuck if…
- API-driven management
- Horizontally scalable
Watch out for
- Requires MongoDB
- Complex to operate
Frequently asked questions
Is Exim or WildDuck better?
Neither is universally better. WildDuck has the larger community; both share a hard setup difficulty, so the decision comes down to features and licensing.
Are Exim and WildDuck free and open-source?
Yes. Exim is licensed under GPL-2.0 and WildDuck under EUPL-1.2. Both can be self-hosted at no software cost.
Can I run Exim and WildDuck with Docker?
Exim: check the project docs for container support. WildDuck: yes.
Which is lighter on resources, Exim or WildDuck?
Exim has the smaller minimum footprint at 64 MB of RAM, compared to about 1,024 MB for WildDuck. Real-world usage depends on library size, user count, and enabled features.