Nullmailer vs OpenSMTPD
A side-by-side comparison of two self-hosted mail servers options — licensing, setup difficulty, resource needs, and what each one replaces.
Not the right match-up?
Nullmailer
Simple relay-only mail transfer agent
VS
OpenSMTPD
Secure and simple SMTP server from OpenBSD
| Feature | Nullmailer | OpenSMTPD |
|---|---|---|
| Category | Mail Servers | Mail Servers |
| License | GPL-2.0 | ISC |
| Language | C++ | C |
| Setup difficulty | Easy | Medium |
| Min. RAM | 16 MB | 32 MB |
| Deployment | bare-metal, source | bare-metal, source |
| GitHub stars | ★ 199 | ★ 579 |
| First released | 2000 | 2013 |
| Replaces | Sendmail | Sendmail, Postfix |
Why pick each one
Frequently asked questions
Is Nullmailer or OpenSMTPD better?
Neither is universally better. OpenSMTPD has the larger community, while Nullmailer is simpler to set up (easy difficulty). Choose based on the comparison table above and your own setup.
Are Nullmailer and OpenSMTPD free and open-source?
Yes. Nullmailer is licensed under GPL-2.0 and OpenSMTPD under ISC. Both can be self-hosted at no software cost.
Can I run Nullmailer and OpenSMTPD with Docker?
Nullmailer: check the project docs for container support. OpenSMTPD: check the project docs for container support.