hMailServer

Projects that follow the best practices below can voluntarily self-certify and show that they've achieved an Open Source Security Foundation (OpenSSF) best practices badge.

There is no set of practices that can guarantee that software will never have defects or vulnerabilities; even formal methods can fail if the specifications or assumptions are wrong. Nor is there any set of practices that can guarantee that a project will sustain a healthy and well-functioning development community. However, following best practices can help improve the results of projects. For example, some practices enable multi-person review before release, which can both help find otherwise hard-to-find technical vulnerabilities and help build trust and a desire for repeated interaction among developers from different companies. To earn a badge, all MUST and MUST NOT criteria must be met, all SHOULD criteria must be met OR be unmet with justification, and all SUGGESTED criteria must be met OR unmet (we want them considered at least). If you want to enter justification text as a generic comment, instead of being a rationale that the situation is acceptable, start the text block with '//' followed by a space. Feedback is welcome via the GitHub site as issues or pull requests There is also a mailing list for general discussion.

We gladly provide the information in several locales, however, if there is any conflict or inconsistency between the translations, the English version is the authoritative version.
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These are the Gold level criteria. You can also view the Passing or Silver level criteria.

Baseline Series: Baseline Level 1 Baseline Level 2 Baseline Level 3

        

 Basics 3/5 ●

  • General

    Note that other projects may use the same name.

    hMailServer is a free, open source email server for Microsoft Windows, implementing SMTP, IMAP and POP3. This is a maintained fork brought up to date with a current toolchain, current cryptography, and the transport-security and authentication standards expected of a mail server in 2026.

    Please use SPDX license expression format; examples include "Apache-2.0", "BSD-2-Clause", "BSD-3-Clause", "GPL-2.0+", "LGPL-3.0+", "MIT", and "(BSD-2-Clause OR Ruby)". Do not include single quotes or double quotes.
    If there is more than one language, list them as comma-separated values (spaces optional) and sort them from most to least used. If there is a long list, please list at least the first three most common ones. If there is no language (e.g., this is a documentation-only or test-only project), use the single character "-". Please use a conventional capitalization for each language, e.g., "JavaScript".
    The Common Platform Enumeration (CPE) is a structured naming scheme for information technology systems, software, and packages. It is used in a number of systems and databases when reporting vulnerabilities.

  • Prerequisites


    Not enough for a badge.

    The project MUST achieve a silver level badge. [achieve_silver]

  • Project oversight


    Enough for a badge!

    The project MUST have a "bus factor" of 2 or more. (URL required) [bus_factor]
    A "bus factor" (aka "truck factor") is the minimum number of project members that have to suddenly disappear from a project ("hit by a bus") before the project stalls due to lack of knowledgeable or competent personnel. The truck-factor tool can estimate this for projects on GitHub. For more information, see Assessing the Bus Factor of Git Repositories by Cosentino et al.

    The project has two maintainers with full access, both able to release and to merge: https://github.com/Progressiverobot/hmailserver/blob/master/GOVERNANCE.md. Every change is reviewed by the other maintainer under the master ruleset, so both know the codebase as it changes.


    Not enough for a badge.

    The project MUST have at least two unassociated significant contributors. (URL required) [contributors_unassociated]
    Contributors are associated if they are paid to work by the same organization (as an employee or contractor) and the organization stands to benefit from the project's results. Financial grants do not count as being from the same organization if they pass through other organizations (e.g., science grants paid to different organizations from a common government or NGO source do not cause contributors to be associated). Someone is a significant contributor if they have made non-trivial contributions to the project in the past year. Examples of good indicators of a significant contributor are: written at least 1,000 lines of code, contributed 50 commits, or contributed at least 20 pages of documentation.

    There are not two unassociated significant contributors. In the past year essentially all human contributions come from one person, Christopher Holloway (494 commits); the only other committer is dependabot[bot] with 4 automated dependency commits, which is neither human nor significant. No second individual has contributed 1,000+ lines, 50+ commits, or substantial documentation. See https://github.com/Progressiverobot/hmailserver/graphs/contributors


  • Other


    Enough for a badge!

    The project MUST include a license statement in each source file. This MAY be done by including the following inside a comment near the beginning of each file: SPDX-License-Identifier: [SPDX license expression for project]. [license_per_file]
    This MAY also be done by including a statement in natural language identifying the license. The project MAY also include a stable URL pointing to the license text, or the full license text. Note that the criterion license_location requires the project license be in a standard location. See this SPDX tutorial for more information about SPDX license expressions. Note the relationship with copyright_per_file, whose content would typically precede the license information.

    Every project source file carries 'SPDX-License-Identifier: AGPL-3.0-or-later' in its header, enforced in CI on every push and pull request by build/add-license-headers.py --check (the required check 'SPDX identifier on every source file'). The exceptions are the 11 vendored zlib 1.3.1 headers under hmailserver/source/Server/zlib, which carry zlib's own license notice in zlib.h. https://github.com/Progressiverobot/hmailserver/blob/master/.github/workflows/style.yml


 Change Control 4/4 ●

  • Public version-controlled source repository


    Enough for a badge!

    The project's source repository MUST use a common distributed version control software (e.g., git or mercurial). [repo_distributed]
    Git is not specifically required and projects can use centralized version control software (such as subversion) with justification.

    Repository on GitHub, which uses git. git is distributed.


    Enough for a badge!

    The project MUST clearly identify small tasks that can be performed by new or casual contributors. (URL required) [small_tasks]
    This identification is typically done by marking selected issues in an issue tracker with one or more tags the project uses for the purpose, e.g., up-for-grabs, first-timers-only, "Small fix", microtask, or IdealFirstBug. These new tasks need not involve adding functionality; they can be improving documentation, adding test cases, or anything else that aids the project and helps the contributor understand more about the project.

    Small tasks for new or casual contributors carry the 'good first issue' label: https://github.com/Progressiverobot/hmailserver/labels/good%20first%20issue - a new webmail language catalogue, screenshots for the README, a page documenting the webmail's keyboard shortcuts and search operators - each with the files to touch and the check to run named in the issue.


    Enough for a badge!

    The project MUST require two-factor authentication (2FA) for developers for changing a central repository or accessing sensitive data (such as private vulnerability reports). This 2FA mechanism MAY use mechanisms without cryptographic mechanisms such as SMS, though that is not recommended. [require_2FA]

    Every account that can change the repository or access sensitive data uses two-factor authentication. Exactly one account holds write access — the maintainer (chrisholloway5, repository admin) — and it has a cryptographic second factor (authenticator app / passkey) enabled; the one other collaborator is read-only. GitHub enforces the MFA challenge at authentication, and has required 2FA for active code contributors platform-wide since 2023. See https://github.com/Progressiverobot/hmailserver/blob/master/GOVERNANCE.md


    Enough for a badge!

    The project's two-factor authentication (2FA) SHOULD use cryptographic mechanisms to prevent impersonation. Short Message Service (SMS) based 2FA, by itself, does NOT meet this criterion, since it is not encrypted. [secure_2FA]
    A 2FA mechanism that meets this criterion would be a Time-based One-Time Password (TOTP) application that automatically generates an authentication code that changes after a certain period of time. Note that GitHub supports TOTP.

    The 2FA mechanism in use on the sole write-access account is cryptographic — an authenticator app / passkey (TOTP or WebAuthn), not SMS. WebAuthn passkeys additionally resist phishing by origin-binding the credential. See https://github.com/Progressiverobot/hmailserver/blob/master/GOVERNANCE.md


 Quality 3/7 ●

  • Coding standards


    Enough for a badge!

    The project MUST document its code review requirements, including how code review is conducted, what must be checked, and what is required to be acceptable. (URL required) [code_review_standards]
    See also two_person_review and contribution_requirements.

    The code review requirements are documented in two places that together cover what is checked, how, and what is acceptable: CONTRIBUTING.md and the pull request template require a warning-free build (/WX and -warnaserror), a green regression suite, regression tests for behaviour changes, exclusively parameterised SQL, focused single-purpose changes, and database scripts for all supported backends; GOVERNANCE.md documents how review is conducted — the maintainer reviews and merges all pull requests, with reasoning recorded in the PR, the issue, or the release notes. See https://github.com/Progressiverobot/hmailserver/blob/master/.github/CONTRIBUTING.md


    Not enough for a badge.

    The project MUST have at least 50% of all proposed modifications reviewed before release by a person other than the author, to determine if it is a worthwhile modification and free of known issues which would argue against its inclusion [two_person_review]

    The master ruleset (https://github.com/Progressiverobot/hmailserver/rules/21165267) requires an approving review by someone other than the author, with re-approval after any later push. It has been in force since 11 September 2026, but on 12 September 2026 the owner merged the webmail waves for the 6.4 release with an administrator bypass because the second maintainer was unavailable, so fewer than half of this release's proposed modifications were reviewed by a second person before release. The criterion is claimed only once a release ships whose changes were all reviewed under the rule.


  • Working build system


    Not enough for a badge.

    The project MUST have a reproducible build. If no building occurs (e.g., scripting languages where the source code is used directly instead of being compiled), select "not applicable" (N/A). (URL required) [build_reproducible]
    A reproducible build means that multiple parties can independently redo the process of generating information from source files and get exactly the same bit-for-bit result. In some cases, this can be resolved by forcing some sort order. JavaScript developers may consider using npm shrinkwrap and webpack OccurrenceOrderPlugin. GCC and clang users may find the -frandom-seed option useful. The build environment (including the toolset) can often be defined for external parties by specifying the cryptographic hash of a specific container or virtual machine that they can use for rebuilding. The reproducible builds project has documentation on how to do this.

    Repeatable on one machine but not yet reproducible across machines. Two clean builds of the same tree on the same toolchain produce a byte-identical hMailServer.exe (/Brepro, /d1trimfile; verified 22 August and 11 September 2026). The hosted CI build of commit e80fc3c60 (MSVC 14.51.36247 on a GitHub-hosted runner) and a local build of the same sources (MSVC 14.51.36231) produce hMailServer.exe files of the same size, 12,155,904 bytes, with different SHA-256 hashes: the compiler patch level differs. Pinning the exact toolchain in both places and publishing the hash is the remaining step; until then release integrity rests on the Sigstore signatures and SLSA provenance attached to every asset.


  • Automated test suite


    Enough for a badge!

    A test suite MUST be invocable in a standard way for that language. (URL required) [test_invocation]
    For example, "make check", "mvn test", or "rake test" (Ruby).

    Tests are invoked via build/run-tests.ps1 scripts in the build/ directory and run automatically in CI. See https://github.com/Progressiverobot/hmailserver/tree/master/build


    Enough for a badge!

    The project MUST implement continuous integration, where new or changed code is frequently integrated into a central code repository and automated tests are run on the result. (URL required) [test_continuous_integration]
    In most cases this means that each developer who works full-time on the project integrates at least daily.

    GitHub Actions runs on every push and pull request to master: the .NET Control Panel test suite with code coverage, a build of the tools solution, and CodeQL analysis, all with warnings treated as errors. The full native regression suite (build/run-tests.ps1) runs as a separate workflow-dispatch job on a self-hosted Windows runner, because it requires the COM server registered, the Windows service deployed, and a live database. See https://github.com/Progressiverobot/hmailserver/blob/master/.github/workflows/ci.yml


    Not enough for a badge.

    The project MUST have FLOSS automated test suite(s) that provide at least 90% statement coverage if there is at least one FLOSS tool that can measure this criterion in the selected language. [test_statement_coverage90]

    Statement coverage of 90% is not demonstrated. Coverage is measured only for the C# Control Panel tests (cobertura in CI); the native C++ server — the bulk of the codebase — has no coverage measurement at all, even though FLOSS tools capable of measuring MSVC-built C++ coverage exist (e.g. OpenCppCoverage), so N/A is not available. The regression suite is broad (SMTP/IMAP/POP3/TLS/auth against a live server) but its statement coverage is unquantified, and no 90% figure can honestly be claimed. See https://github.com/Progressiverobot/hmailserver/blob/master/.github/workflows/ci.yml


    Not enough for a badge.

    The project MUST have FLOSS automated test suite(s) that provide at least 80% branch coverage if there is at least one FLOSS tool that can measure this criterion in the selected language. [test_branch_coverage80]

    Branch coverage of 80% is not demonstrated. Branch coverage is not reported even for the C# code (CI collects cobertura statement/line data for the Control Panel tests only), and the native C++ server has no coverage measurement of any kind, despite FLOSS tools existing that can measure coverage of MSVC-built code (e.g. OpenCppCoverage), so N/A is not available. No branch-coverage figure exists to support a claim. See https://github.com/Progressiverobot/hmailserver/blob/master/.github/workflows/ci.yml


 Security 5/5 ●

  • Use basic good cryptographic practices

    Note that some software does not need to use cryptographic mechanisms. If your project produces software that (1) includes, activates, or enables encryption functionality, and (2) might be released from the United States (US) to outside the US or to a non-US-citizen, you may be legally required to take a few extra steps. Typically this just involves sending an email. For more information, see the encryption section of Understanding Open Source Technology & US Export Controls.

    Enough for a badge!

    The software produced by the project MUST support secure protocols for all of its network communications, such as SSHv2 or later, TLS1.2 or later (HTTPS), IPsec, SFTP, and SNMPv3. Insecure protocols such as FTP, HTTP, telnet, SSLv3 or earlier, and SSHv1 MUST be disabled by default, and only enabled if the user specifically configures it. If the software produced by the project does not support network communications, select "not applicable" (N/A). [crypto_used_network]

    All network communications support secure protocols. SMTP, IMAP and POP3 are each offered with STARTTLS and with implicit TLS, the REST API and web-services listeners run over HTTPS, and the server implements the transport-security standards expected of a modern MTA, including DANE, MTA-STS and per-route TLS policy. See https://github.com/Progressiverobot/hmailserver/blob/master/hmailserver/source/Server/SMTP/TlsPolicy.cpp


    Enough for a badge!

    The software produced by the project MUST, if it supports or uses TLS, support at least TLS version 1.2. Note that the predecessor of TLS was called SSL. If the software does not use TLS, select "not applicable" (N/A). [crypto_tls12]

    TLS 1.2 and TLS 1.3 are both supported and are the versions offered by default; older protocol versions are individually controlled through the SSL_OP_NO_* options and the obsolete ones are disabled. Release validation exercises TLS 1.2 and 1.3 handshakes end to end against the exact binary being shipped. See https://github.com/Progressiverobot/hmailserver/blob/master/hmailserver/source/Server/Common/TCPIP/SslContextInitializer.cpp


  • Secured delivery against man-in-the-middle (MITM) attacks


    Enough for a badge!

    The project website, repository (if accessible via the web), and download site (if separate) MUST include key hardening headers with nonpermissive values. (URL required) [hardened_site]
    Note that GitHub and GitLab are known to meet this. Sites such as https://securityheaders.com/ can quickly check this. The key hardening headers are: Content Security Policy (CSP), HTTP Strict Transport Security (HSTS), X-Content-Type-Options (as "nosniff"), and X-Frame-Options. Fully static web sites with no ability to log in via the web pages could omit some hardening headers with less risk, but there's no reliable way to detect such sites, so we require these headers even if they are fully static sites.

    https://www.progressiverobot.com/hmailserver-services/ sends Content-Security-Policy (object-src none; base-uri self; frame-ancestors self; upgrade-insecure-requests), Strict-Transport-Security with preload and includeSubDomains, X-Content-Type-Options: nosniff, X-Frame-Options: SAMEORIGIN, Referrer-Policy: same-origin, Cross-Origin-Opener-Policy: same-origin and a Permissions-Policy that disables the sensors, checked on 11 September 2026. The repository and the download site are GitHub, which sends its own hardened headers.


  • Other security issues


    Enough for a badge!

    The project MUST have performed a security review within the last 5 years. This review MUST consider the security requirements and security boundary. [security_review]
    This MAY be done by the project members and/or an independent evaluation. This evaluation MAY be supported by static and dynamic analysis tools, but there also must be human review to identify problems (particularly in design) that tools cannot detect.

    A security review of the current codebase was performed and documented in 2026, well within 5 years: ASSURANCE-CASE.md records the security requirements as explicit claims (C1-C7), the threat model and security boundary (trust boundaries B1-B6, with the administrative boundary explicitly drawn), the argument that secure design principles are applied, CWE-mapped analysis of implementation weaknesses and their countermeasures, and the residual risks. It is backed by continuous CodeQL analysis, OpenSSF Scorecard, and the libFuzzer harness suite under fuzz/. See https://github.com/Progressiverobot/hmailserver/blob/master/ASSURANCE-CASE.md


    Enough for a badge!

    Hardening mechanisms MUST be used in the software produced by the project so that software defects are less likely to result in security vulnerabilities. (URL required) [hardening]
    Hardening mechanisms may include HTTP headers like Content Security Policy (CSP), compiler flags to mitigate attacks (such as -fstack-protector), or compiler flags to eliminate undefined behavior. For our purposes least privilege is not considered a hardening mechanism (least privilege is important, but separate).

    The native binaries are built with the MSVC hardening defaults left in place rather than disabled: /GS buffer security checks, DEP (/NXCOMPAT) and ASLR (/DYNAMICBASE) are all active for the x64 Release configuration. Control Flow Guard is not currently enabled and is a candidate for a future build change. Beyond compiler hardening, the server refuses unsafe password-hash schemes for new secrets and verifies TLS peers by default. See https://github.com/Progressiverobot/hmailserver/blob/master/hmailserver/source/Server/hMailServer/hMailServer.vcxproj


 Analysis 2/2 ●

  • Dynamic code analysis


    Enough for a badge!

    The project MUST apply at least one dynamic analysis tool to any proposed major production release of the software produced by the project before its release. [dynamic_analysis]
    A dynamic analysis tool examines the software by executing it with specific inputs. For example, the project MAY use a fuzzing tool (e.g., American Fuzzy Lop) or a web application scanner (e.g., OWASP ZAP or w3af). In some cases the OSS-Fuzz project may be willing to apply fuzz testing to your project. For purposes of this criterion the dynamic analysis tool needs to vary the inputs in some way to look for various kinds of problems or be an automated test suite with at least 80% branch coverage. The Wikipedia page on dynamic analysis and the OWASP page on fuzzing identify some dynamic analysis tools. The analysis tool(s) MAY be focused on looking for security vulnerabilities, but this is not required.

    Before every release the full regression suite (2,175 tests, driving a running server over SMTP, IMAP, POP3 and REST) runs against the assertion build of the server - build.ps1 -Asserts keeps every HM_ASSERT in a Release build and a violated assertion is reported as HM6364 in the error log and fails the gate (RELEASE.md step 8b) - and then against the plain Release build. Coverage-guided libFuzzer harnesses for the MIME parsers live under fuzz/ (clang -fsanitize=fuzzer,address, seed corpora, a dictionary and a committed regression corpus of fixed findings), and hmailserver/docs/Fuzzing.md prescribes a fuzz run before a release that changed message handling. https://github.com/Progressiverobot/hmailserver/blob/master/RELEASE.md


    Enough for a badge!

    The project SHOULD include many run-time assertions in the software it produces and check those assertions during dynamic analysis. [dynamic_analysis_enable_assertions]
    This criterion does not suggest enabling assertions during production; that is entirely up to the project and its users to decide. This criterion's focus is instead to improve fault detection during dynamic analysis before deployment. Enabling assertions in production use is completely different from enabling assertions during dynamic analysis (such as testing). In some cases enabling assertions in production use is extremely unwise (especially in high-integrity components). There are many arguments against enabling assertions in production, e.g., libraries should not crash callers, their presence may cause rejection by app stores, and/or activating an assertion in production may expose private data such as private keys. Beware that in many Linux distributions NDEBUG is not defined, so C/C++ assert() will by default be enabled for production in those environments. It may be important to use a different assertion mechanism or defining NDEBUG for production in those environments.

    The release gate runs the whole regression suite on the assertion build (build.ps1 -Configuration Release -Asserts), in which every HM_ASSERT stays enabled; a violated assertion is logged as HM6364 and fails the run. RELEASE.md step 8b makes this run precede the plain Release gate. https://github.com/Progressiverobot/hmailserver/blob/master/RELEASE.md



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Project badge entry owned by: Progressive Robot.
Entry created on 2026-08-21 05:37:27 UTC, last updated on 2026-09-12 02:50:23 UTC. Last achieved passing badge on 2026-08-21 17:17:16 UTC.