Postfix vs Exim
A side-by-side comparison of two self-hosted mail servers options — licensing, setup difficulty, resource needs, and what each one replaces.
| Feature | Postfix | Exim |
|---|---|---|
| Deploy effort | Under-an-hour setup | Read-the-docs project |
| Health score | 75 · Good | 15 · At risk |
| Status | Actively maintained | Archived |
| Category | Mail Servers | Mail Servers |
| License | IPL-1.0 | GPL-2.0 |
| Language | C | C |
| Setup difficulty | Hard | Hard |
| Min. RAM | 128 MB | 64 MB |
| Deployment | docker, bare-metal, source | bare-metal, source |
| GitHub stars | ★ 576 | ★ 785 |
| First released | 1998 | 1995 |
| Replaces | Microsoft Exchange | Microsoft Exchange |
What are Postfix and Exim?
Postfix
Postfix is a widely deployed mail transfer agent that routes and delivers email. It is the SMTP backbone of countless self-hosted mail servers thanks to its security and performance.
- High-performance SMTP server
- Strong security architecture
- Flexible routing and policy
- De facto standard MTA
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
Postfix vs Exim: key differences
The biggest difference is maintenance: Exim's repository is archived and no longer developed, while Postfix is actively maintained. Both projects are written in C. Licensing differs — IPL-1.0 for Postfix versus GPL-2.0 for Exim. Exim is the lighter option, starting around 64 MB of RAM against 128 MB for Postfix. Exim is the more established project (first released 1995), while Postfix arrived in 1998. Postfix lists first-class Docker deployment; Exim does not.
Why pick each one
Choose Postfix if…
- Battle-tested and stable
- Extensive documentation
Watch out for
- Configuration has a steep curve
- Only handles mail transfer
Choose Exim if…
- Extremely flexible
- Proven at scale
Watch out for
- Complex configuration
- Easy to misconfigure
Frequently asked questions
Is Postfix or Exim better?
Neither is universally better. Exim has the larger community; both share a hard setup difficulty, so the decision comes down to features and licensing.
Are Postfix and Exim free and open-source?
Yes. Postfix is licensed under IPL-1.0 and Exim under GPL-2.0. Both can be self-hosted at no software cost.
Can I run Postfix and Exim with Docker?
Postfix: yes. Exim: check the project docs for container support.
Which is lighter on resources, Postfix or Exim?
Exim has the smaller minimum footprint at 64 MB of RAM, compared to about 128 MB for Postfix. Real-world usage depends on library size, user count, and enabled features.