---
title: "NET-MAIL-001 Postfix SMTP TLS Not Offered or Has No Certificate"
canonical: https://openvapt.com/checks/NET-MAIL-001.html
html: https://openvapt.com/checks/NET-MAIL-001.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-MAIL-001 Postfix SMTP TLS Not Offered or Has No Certificate

smtpd_tls_security_level is none or unset, or is may or encrypt without a server certificate, so incoming SMTP sessions cannot be encrypted.

- Domain: Network
- Severity: Medium
- Control category: Cryptography and TLS
- Fix effort: low
- CVSS v3.1 vector: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N`
- CIS Controls v8: 3.10
- NIST CSF 2.0: PR.DS-02
- CWE: CWE-319
- OWASP Top 10 2021: A02:2021
- OWASP ASVS 4.0.3: 9.2.2
- NIST SP 800-53 Rev. 5: SC-8, SC-13
- Benchmark topic: Mail transport encryption (topic only, no benchmark text)

## Why It Matters

Without STARTTLS every message and every authentication exchange that other servers and clients send to this host crosses the network in the clear. Opportunistic TLS (may) with a valid certificate is the baseline that other mail servers expect.

## How It Detects

Reads main.cf for smtpd_tls_security_level (or the legacy smtpd_use_tls) and smtpd_tls_cert_file or smtpd_tls_chain_files. Fails when the level is none or unset, or when TLS is enabled but no certificate file is named.

## How to Fix

Set  smtpd_tls_security_level = may ,  smtpd_tls_chain_files = /etc/letsencrypt/live/<host>/privkey.pem, /etc/letsencrypt/live/<host>/fullchain.pem  (or smtpd_tls_cert_file and smtpd_tls_key_file), then postfix reload.

## How to Verify

```
postconf smtpd_tls_security_level smtpd_tls_chain_files  and an authorised  openssl s_client -starttls smtp -connect 127.0.0.1:25  showing a certificate.
```

## Learn the Theory

- [P19 Database, Mail and DNS Hardening](https://openvapt.com/academy/p19.md)

## References

- [Postfix TLS Support](https://www.postfix.org/TLS_README.html)
- [Postfix Configuration Parameters](https://www.postfix.org/postconf.5.html)
- [NIST SP 800-177 Rev. 1, Trustworthy Email](https://csrc.nist.gov/pubs/sp/800/177/r1/final)

## Source Code

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

Run it: `openvapt scan --only NET-MAIL-001`. Read it offline: `openvapt explain NET-MAIL-001`.

---

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