---
title: "NET-DB-012 Postfix Open Relay Controls"
canonical: https://openvapt.com/checks/NET-DB-012.html
html: https://openvapt.com/checks/NET-DB-012.html
site: OpenVAPT, https://openvapt.com/
license: OpenVAPT Source-Available Licence 1.3, https://openvapt.com/legal/licence-text.html
modified: 2026-10-14
version: 0.1.0-alpha.6
---

# NET-DB-012 Postfix Open Relay Controls

Postfix relay restrictions are missing or mynetworks trusts overly broad ranges.

- Domain: Network
- Severity: High
- Control category: Data Services
- Fix effort: low
- CVSS v3.1 vector: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L`
- CIS Controls v8: 4.1
- NIST CSF 2.0: PR.PS-01
- CWE: CWE-441
- OWASP Top 10 2021: A05:2021
- NIST SP 800-53 Rev. 5: AC-3, CM-6, SC-7
- Benchmark topic: Secure data service configuration (topic only, no benchmark text)

## Why It Matters

An open relay enables spam and phishing, damages domain reputation, and can expose the host to blocklisting.

## How It Detects

Parses main.cf for smtpd_relay_restrictions with reject_unauth_destination and flags 0.0.0.0/0 or ::/0 in mynetworks.

## How to Fix

Set smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination and narrow mynetworks.

## How to Verify

```
Run postconf -n during approved administration and perform only an authorized relay test.
```

## Learn the Theory

- [P3 Network Exposure and Firewalls](https://openvapt.com/academy/p3.md)
- [P8 Data Services: Databases, File Shares, DNS and Mail](https://openvapt.com/academy/p8.md)

## References

- [Postfix SMTP Relay and Access Control](https://www.postfix.org/SMTPD_ACCESS_README.html)

## Source Code

https://github.com/OpenVAPT/openvapt/blob/574f7f3333c44b75a3c649e2d93a76d507f75adf/internal/checks/network/services.go

Run it: `openvapt scan --only NET-DB-012`. Read it offline: `openvapt explain NET-DB-012`.

---

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