chore(deps): update module github.com/oapi-codegen/oapi-codegen/v2 to v2.6.0

Use DNS records instead of authentication results to determine DKIM
presence, enabling a three-state display: passed (green), published but
invalid signature (yellow+red), or no DKIM at all (red).

README.md

@@ -166,7 +166,24 @@ The server will start on `http://localhost:8080` by default.
 It is expected your setup annotate the email with eg. opendkim, spamassassin, rspamd, ...
 happyDeliver will not perform thoses checks, it relies instead on standard software to have real world annotations.
 
-Choose one of the following way to integrate happyDeliver in your existing setup:
+#### Receiver Hostname
+
+happyDeliver filters `Authentication-Results` headers by hostname to only trust headers added by your MTA (and not headers that may have been injected by the sender). By default, it uses the system hostname (`os.Hostname()`).
+
+If your MTA's `authserv-id` (the hostname at the beginning of `Authentication-Results` headers) differs from the machine running happyDeliver, you must set it explicitly:
+
+```bash
+./happyDeliver server -receiver-hostname mail.example.com
+```
+
+Or via environment variable:
+```bash
+HAPPYDELIVER_RECEIVER_HOSTNAME=mail.example.com ./happyDeliver server
+```
+
+**How to find the correct value:** look at the `Authentication-Results` headers in a received email. They start with the authserv-id, e.g. `Authentication-Results: mail.example.com; spf=pass ...` — in this case, use `mail.example.com`.
+
+If the value is misconfigured, happyDeliver will log a warning when the last `Received` hop doesn't match the expected hostname.
 
 #### Postfix LMTP Transport
 

docker/README.md

@@ -110,14 +110,38 @@ Default configuration for the Docker environment:
 The container accepts these environment variables:
 
 - `HAPPYDELIVER_DOMAIN`: Email domain for test addresses (default: happydeliver.local)
+- `HAPPYDELIVER_RECEIVER_HOSTNAME`: Hostname used to filter `Authentication-Results` headers (see below)
+- `POSTFIX_CERT_FILE` / `POSTFIX_KEY_FILE`: TLS certificate and key paths for Postfix SMTP
 
-Note that the hostname of the container is used to filter the authentication tests results.
+### Receiver Hostname
 
-Example:
+happyDeliver filters `Authentication-Results` headers by hostname to only trust results from the expected MTA. By default, it uses the system hostname (i.e., the container's `--hostname`).
+
+In the all-in-one Docker container, the container hostname is also used as the `authserv-id` in the embedded Postfix and authentication_milter, so everything matches automatically.
+
+**When bypassing the embedded Postfix** (e.g., routing emails from your own MTA via LMTP), your MTA's `authserv-id` will likely differ from the container hostname. In that case, set `HAPPYDELIVER_RECEIVER_HOSTNAME` to your MTA's hostname:
+
+```bash
+docker run -d \
+  -e HAPPYDELIVER_DOMAIN=example.com \
+  -e HAPPYDELIVER_RECEIVER_HOSTNAME=mail.example.com \
+  ...
+```
+
+To find the correct value, look at the `Authentication-Results` headers in a received email — they start with the authserv-id, e.g. `Authentication-Results: mail.example.com; spf=pass ...`.
+
+If the value is misconfigured, happyDeliver will log a warning when the last `Received` hop doesn't match the expected hostname.
+
+Example (all-in-one, no override needed):
 ```bash
 docker run -e HAPPYDELIVER_DOMAIN=example.com --hostname mail.example.com ...
 ```
 
+Example (external MTA integration):
+```bash
+docker run -e HAPPYDELIVER_DOMAIN=example.com -e HAPPYDELIVER_RECEIVER_HOSTNAME=mail.example.com ...
+```
+
 ## Volumes
 
 **Required volumes:**

go.mod

@@ -49,7 +49,7 @@ require (
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/mohae/deepcopy v0.0.0-20170929034955-c48cc78d4826 // indirect
-	github.com/oapi-codegen/oapi-codegen/v2 v2.5.1 // indirect
+	github.com/oapi-codegen/oapi-codegen/v2 v2.6.0 // indirect
 	github.com/oasdiff/yaml v0.0.0-20250309154309-f31be36b4037 // indirect
 	github.com/oasdiff/yaml3 v0.0.0-20250309153720-d2182401db90 // indirect
 	github.com/pelletier/go-toml/v2 v2.2.4 // indirect

go.sum

@@ -125,8 +125,8 @@ github.com/mohae/deepcopy v0.0.0-20170929034955-c48cc78d4826/go.mod h1:TaXosZuwd
 github.com/nxadm/tail v1.4.4/go.mod h1:kenIhsEOeOJmVchQTgglprH7qJGnHDVpk1VPCcaMI8A=
 github.com/nxadm/tail v1.4.8 h1:nPr65rt6Y5JFSKQO7qToXr7pePgD6Gwiw05lkbyAQTE=
 github.com/nxadm/tail v1.4.8/go.mod h1:+ncqLTQzXmGhMZNUePPaPqPvBxHAIsmXswZKocGu+AU=
-github.com/oapi-codegen/oapi-codegen/v2 v2.5.1 h1:5vHNY1uuPBRBWqB2Dp0G7YB03phxLQZupZTIZaeorjc=
+github.com/oapi-codegen/oapi-codegen/v2 v2.6.0 h1:4i+F2cvwBFZeplxCssNdLy3MhNzUD87mI3HnayHZkAU=
-github.com/oapi-codegen/oapi-codegen/v2 v2.5.1/go.mod h1:ro0npU1BWkcGpCgGD9QwPp44l5OIZ94tB3eabnT7DjQ=
+github.com/oapi-codegen/oapi-codegen/v2 v2.6.0/go.mod h1:eWHeJSohQJIINJZzzQriVynfGsnlQVh0UkN2UYYcw4Q=
 github.com/oapi-codegen/runtime v1.3.0 h1:vyK1zc0gDWWXgk2xoQa4+X4RNNc5SL2RbTpJS/4vMYA=
 github.com/oapi-codegen/runtime v1.3.0/go.mod h1:kOdeacKy7t40Rclb1je37ZLFboFxh+YLy0zaPCMibPY=
 github.com/oasdiff/yaml v0.0.0-20250309154309-f31be36b4037 h1:G7ERwszslrBzRxj//JalHPu/3yz+De2J+4aLtSRlHiY=

internal/config/cli.go

@@ -34,6 +34,7 @@ func declareFlags(o *Config) {
 	flag.StringVar(&o.Email.Domain, "domain", o.Email.Domain, "Domain used to receive emails")
 	flag.StringVar(&o.Email.TestAddressPrefix, "address-prefix", o.Email.TestAddressPrefix, "Expected email adress prefix (deny address that doesn't start with this prefix)")
 	flag.StringVar(&o.Email.LMTPAddr, "lmtp-addr", o.Email.LMTPAddr, "LMTP server listen address")
+	flag.StringVar(&o.Email.ReceiverHostname, "receiver-hostname", o.Email.ReceiverHostname, "Hostname used to filter Authentication-Results headers (defaults to os.Hostname())")
 	flag.DurationVar(&o.Analysis.DNSTimeout, "dns-timeout", o.Analysis.DNSTimeout, "Timeout when performing DNS query")
 	flag.DurationVar(&o.Analysis.HTTPTimeout, "http-timeout", o.Analysis.HTTPTimeout, "Timeout when performing HTTP query")
 	flag.Var(&StringArray{&o.Analysis.RBLs}, "rbl", "Append a RBL (use this option multiple time to append multiple RBLs)")

internal/config/config.go

@@ -34,6 +34,11 @@ import (
 	openapi_types "github.com/oapi-codegen/runtime/types"
 )
 
+func getHostname() string {
+	h, _ := os.Hostname()
+	return h
+}
+
 // Config represents the application configuration
 type Config struct {
 	DevProxy        string
@@ -58,6 +63,7 @@ type EmailConfig struct {
 	Domain            string
 	TestAddressPrefix string
 	LMTPAddr          string
+	ReceiverHostname  string
 }
 
 // AnalysisConfig contains timeout and behavior settings for email analysis
@@ -84,6 +90,7 @@ func DefaultConfig() *Config {
 			Domain:            "happydeliver.local",
 			TestAddressPrefix: "test-",
 			LMTPAddr:          "127.0.0.1:2525",
+			ReceiverHostname:  getHostname(),
 		},
 		Analysis: AnalysisConfig{
 			DNSTimeout:  5 * time.Second,

internal/receiver/receiver.go

@@ -98,6 +98,17 @@ func (r *EmailReceiver) ProcessEmailBytes(rawEmail []byte, recipientEmail string
 
 	log.Printf("Analysis complete. Grade: %s. Score: %d/100", result.Report.Grade, result.Report.Score)
 
+	// Warn if the last Received hop doesn't match the expected receiver hostname
+	if r.config.Email.ReceiverHostname != "" &&
+		result.Report.HeaderAnalysis != nil &&
+		result.Report.HeaderAnalysis.ReceivedChain != nil &&
+		len(*result.Report.HeaderAnalysis.ReceivedChain) > 0 {
+		lastHop := (*result.Report.HeaderAnalysis.ReceivedChain)[0]
+		if lastHop.By != nil && *lastHop.By != r.config.Email.ReceiverHostname {
+			log.Printf("WARNING: Last Received hop 'by' field (%s) does not match expected receiver hostname (%s): check your RECEIVER_HOSTNAME config as authentication results will be false", *lastHop.By, r.config.Email.ReceiverHostname)
+		}
+	}
+
 	// Marshal report to JSON
 	reportJSON, err := json.Marshal(result.Report)
 	if err != nil {

pkg/analyzer/analyzer.go

@@ -41,6 +41,7 @@ type EmailAnalyzer struct {
 // NewEmailAnalyzer creates a new email analyzer with the given configuration
 func NewEmailAnalyzer(cfg *config.Config) *EmailAnalyzer {
 	generator := NewReportGenerator(
+		cfg.Email.ReceiverHostname,
 		cfg.Analysis.DNSTimeout,
 		cfg.Analysis.HTTPTimeout,
 		cfg.Analysis.RBLs,

pkg/analyzer/authentication.go

@@ -28,11 +28,13 @@ import (
 )
 
 // AuthenticationAnalyzer analyzes email authentication results
-type AuthenticationAnalyzer struct{}
+type AuthenticationAnalyzer struct {
+	receiverHostname string
+}
 
 // NewAuthenticationAnalyzer creates a new authentication analyzer
-func NewAuthenticationAnalyzer() *AuthenticationAnalyzer {
+func NewAuthenticationAnalyzer(receiverHostname string) *AuthenticationAnalyzer {
-	return &AuthenticationAnalyzer{}
+	return &AuthenticationAnalyzer{receiverHostname: receiverHostname}
 }
 
 // AnalyzeAuthentication extracts and analyzes authentication results from email headers
@@ -40,7 +42,7 @@ func (a *AuthenticationAnalyzer) AnalyzeAuthentication(email *EmailMessage) *api
 	results := &api.AuthenticationResults{}
 
 	// Parse Authentication-Results headers
-	authHeaders := email.GetAuthenticationResults()
+	authHeaders := email.GetAuthenticationResults(a.receiverHostname)
 	for _, header := range authHeaders {
 		a.parseAuthenticationResultsHeader(header, results)
 	}

pkg/analyzer/authentication_arc_test.go

@@ -50,7 +50,7 @@ func TestParseARCResult(t *testing.T) {
 		},
 	}
 
-	analyzer := NewAuthenticationAnalyzer()
+	analyzer := NewAuthenticationAnalyzer("")
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -136,7 +136,7 @@ func TestValidateARCChain(t *testing.T) {
 		},
 	}
 
-	analyzer := NewAuthenticationAnalyzer()
+	analyzer := NewAuthenticationAnalyzer("")
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

pkg/analyzer/authentication_bimi_test.go

@@ -64,7 +64,7 @@ func TestParseBIMIResult(t *testing.T) {
 		},
 	}
 
-	analyzer := NewAuthenticationAnalyzer()
+	analyzer := NewAuthenticationAnalyzer("")
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

pkg/analyzer/authentication_dkim_test.go

@@ -58,7 +58,7 @@ func TestParseDKIMResult(t *testing.T) {
 		},
 	}
 
-	analyzer := NewAuthenticationAnalyzer()
+	analyzer := NewAuthenticationAnalyzer("")
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

pkg/analyzer/authentication_dmarc_test.go

@@ -48,7 +48,7 @@ func TestParseDMARCResult(t *testing.T) {
 		},
 	}
 
-	analyzer := NewAuthenticationAnalyzer()
+	analyzer := NewAuthenticationAnalyzer("")
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

pkg/analyzer/authentication_iprev_test.go

@@ -93,7 +93,7 @@ func TestParseIPRevResult(t *testing.T) {
 		},
 	}
 
-	analyzer := NewAuthenticationAnalyzer()
+	analyzer := NewAuthenticationAnalyzer("")
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -181,7 +181,7 @@ func TestParseAuthenticationResultsHeader_IPRev(t *testing.T) {
 		},
 	}
 
-	analyzer := NewAuthenticationAnalyzer()
+	analyzer := NewAuthenticationAnalyzer("")
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

pkg/analyzer/authentication_spf_test.go

@@ -60,7 +60,7 @@ func TestParseSPFResult(t *testing.T) {
 		},
 	}
 
-	analyzer := NewAuthenticationAnalyzer()
+	analyzer := NewAuthenticationAnalyzer("")
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -161,7 +161,7 @@ func TestParseLegacySPF(t *testing.T) {
 		},
 	}
 
-	analyzer := NewAuthenticationAnalyzer()
+	analyzer := NewAuthenticationAnalyzer("")
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

pkg/analyzer/authentication_test.go

@@ -100,7 +100,7 @@ func TestGetAuthenticationScore(t *testing.T) {
 		},
 	}
 
-	scorer := NewAuthenticationAnalyzer()
+	scorer := NewAuthenticationAnalyzer("")
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -247,7 +247,7 @@ func TestParseAuthenticationResultsHeader(t *testing.T) {
 		},
 	}
 
-	analyzer := NewAuthenticationAnalyzer()
+	analyzer := NewAuthenticationAnalyzer("")
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -353,7 +353,7 @@ func TestParseAuthenticationResultsHeader(t *testing.T) {
 
 func TestParseAuthenticationResultsHeader_OnlyFirstResultParsed(t *testing.T) {
 	// This test verifies that only the first occurrence of each auth method is parsed
-	analyzer := NewAuthenticationAnalyzer()
+	analyzer := NewAuthenticationAnalyzer("")
 
 	t.Run("Multiple SPF results - only first is parsed", func(t *testing.T) {
 		header := "mail.example.com; spf=pass smtp.mailfrom=first@example.com; spf=fail smtp.mailfrom=second@example.com"

pkg/analyzer/authentication_x_aligned_from_test.go

@@ -66,7 +66,7 @@ func TestParseXAlignedFromResult(t *testing.T) {
 		},
 	}
 
-	analyzer := NewAuthenticationAnalyzer()
+	analyzer := NewAuthenticationAnalyzer("")
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -126,7 +126,7 @@ func TestCalculateXAlignedFromScore(t *testing.T) {
 		},
 	}
 
-	analyzer := NewAuthenticationAnalyzer()
+	analyzer := NewAuthenticationAnalyzer("")
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

pkg/analyzer/authentication_x_google_dkim_test.go

@@ -60,7 +60,7 @@ func TestParseXGoogleDKIMResult(t *testing.T) {
 		},
 	}
 
-	analyzer := NewAuthenticationAnalyzer()
+	analyzer := NewAuthenticationAnalyzer("")
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

pkg/analyzer/dns.go

@@ -54,7 +54,7 @@ func NewDNSAnalyzerWithResolver(timeout time.Duration, resolver DNSResolver) *DN
 }
 
 // AnalyzeDNS performs DNS validation for the email's domain
-func (d *DNSAnalyzer) AnalyzeDNS(email *EmailMessage, authResults *api.AuthenticationResults, headersResults *api.HeaderAnalysis) *api.DNSResults {
+func (d *DNSAnalyzer) AnalyzeDNS(email *EmailMessage, headersResults *api.HeaderAnalysis) *api.DNSResults {
 	// Extract domain from From address
 	if headersResults.DomainAlignment.FromDomain == nil || *headersResults.DomainAlignment.FromDomain == "" {
 		return &api.DNSResults{
@@ -104,19 +104,14 @@ func (d *DNSAnalyzer) AnalyzeDNS(email *EmailMessage, authResults *api.Authentic
 	// SPF validates the MAIL FROM command, which corresponds to Return-Path
 	results.SpfRecords = d.checkSPFRecords(spfDomain)
 
-	// Check DKIM records (from authentication results)
+	// Check DKIM records by parsing DKIM-Signature headers directly
-	// DKIM can be for any domain, but typically the From domain
+	for _, sig := range parseDKIMSignatures(email.Header["DKIM-Signature"]) {
-	if authResults != nil && authResults.Dkim != nil {
+		dkimRecord := d.checkDKIMRecord(sig.Domain, sig.Selector)
-		for _, dkim := range *authResults.Dkim {
+		if dkimRecord != nil {
-			if dkim.Domain != nil && dkim.Selector != nil {
+			if results.DkimRecords == nil {
-				dkimRecord := d.checkDKIMRecord(*dkim.Domain, *dkim.Selector)
+				results.DkimRecords = new([]api.DKIMRecord)
-				if dkimRecord != nil {
-					if results.DkimRecords == nil {
-						results.DkimRecords = new([]api.DKIMRecord)
-					}
-					*results.DkimRecords = append(*results.DkimRecords, *dkimRecord)
-				}
 			}
+			*results.DkimRecords = append(*results.DkimRecords, *dkimRecord)
 		}
 	}
 

pkg/analyzer/dns_dkim.go

@@ -29,6 +29,38 @@ import (
 	"git.happydns.org/happyDeliver/internal/api"
 )
 
+// DKIMHeader holds the domain and selector extracted from a DKIM-Signature header.
+type DKIMHeader struct {
+	Domain   string
+	Selector string
+}
+
+// parseDKIMSignatures extracts domain and selector from DKIM-Signature header values.
+func parseDKIMSignatures(signatures []string) []DKIMHeader {
+	var results []DKIMHeader
+	for _, sig := range signatures {
+		var domain, selector string
+		for _, part := range strings.Split(sig, ";") {
+			kv := strings.SplitN(strings.TrimSpace(part), "=", 2)
+			if len(kv) != 2 {
+				continue
+			}
+			key := strings.TrimSpace(kv[0])
+			val := strings.TrimSpace(kv[1])
+			switch key {
+			case "d":
+				domain = val
+			case "s":
+				selector = val
+			}
+		}
+		if domain != "" && selector != "" {
+			results = append(results, DKIMHeader{Domain: domain, Selector: selector})
+		}
+	}
+	return results
+}
+
 // checkapi.DKIMRecord looks up and validates DKIM record for a domain and selector
 func (d *DNSAnalyzer) checkDKIMRecord(domain, selector string) *api.DKIMRecord {
 	// DKIM records are at: selector._domainkey.domain

pkg/analyzer/dns_dkim_test.go

@@ -26,6 +26,220 @@ import (
 	"time"
 )
 
+func TestParseDKIMSignatures(t *testing.T) {
+	tests := []struct {
+		name       string
+		signatures []string
+		expected   []DKIMHeader
+	}{
+		{
+			name:       "Empty input",
+			signatures: nil,
+			expected:   nil,
+		},
+		{
+			name:       "Empty string",
+			signatures: []string{""},
+			expected:   nil,
+		},
+		{
+			name: "Simple Gmail-style",
+			signatures: []string{
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:subject:date:message-id; bh=abcdef1234567890=; b=SIGNATURE_DATA_HERE==`,
+			},
+			expected: []DKIMHeader{{Domain: "gmail.com", Selector: "20210112"}},
+		},
+		{
+			name: "Microsoft 365 style",
+			signatures: []string{
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; d=contoso.com; s=selector1; h=From:Date:Subject:Message-ID; bh=UErATeHehIIPIXPeUA==; b=SIGNATURE_DATA==`,
+			},
+			expected: []DKIMHeader{{Domain: "contoso.com", Selector: "selector1"}},
+		},
+		{
+			name: "Tab-folded multiline (Postfix-style)",
+			signatures: []string{
+				"v=1; a=rsa-sha256; c=relaxed/simple; d=nemunai.re; s=thot;\r\n\tt=1760866834; bh=YNB7c8Qgm8YGn9X1FAXTcdpO7t4YSZFiMrmpCfD/3zw=;\r\n\th=From:To:Subject;\r\n\tb=T4TFaypMpsHGYCl3PGLwmzOYRF11rYjC7lF8V5VFU+ldvG8WBpFn==",
+			},
+			expected: []DKIMHeader{{Domain: "nemunai.re", Selector: "thot"}},
+		},
+		{
+			name: "Space-folded multiline (RFC-style)",
+			signatures: []string{
+				"v=1; a=rsa-sha256; c=relaxed/relaxed;\r\n d=football.example.com; i=@football.example.com;\r\n q=dns/txt; s=test; t=1528637909; h=from:to:subject;\r\n bh=2jUSOH9NhtVGCQWNr9BrIAPreKQjO6Sn7XIkfJVOzv8=;\r\n b=F45dVWDfMbQDGHJFlXUNB2HKfbCeLRyhDXgFpEL8Gwps==",
+			},
+			expected: []DKIMHeader{{Domain: "football.example.com", Selector: "test"}},
+		},
+		{
+			name: "d= and s= on separate continuation lines",
+			signatures: []string{
+				"v=1; a=rsa-sha256;\r\n\tc=relaxed/relaxed;\r\n\td=mycompany.com;\r\n\ts=selector1;\r\n\tbh=hash=;\r\n\tb=sig==",
+			},
+			expected: []DKIMHeader{{Domain: "mycompany.com", Selector: "selector1"}},
+		},
+		{
+			name: "No space after semicolons",
+			signatures: []string{
+				`v=1;a=rsa-sha256;c=relaxed/relaxed;d=example.net;s=mail;h=from:to:subject;bh=abc=;b=xyz==`,
+			},
+			expected: []DKIMHeader{{Domain: "example.net", Selector: "mail"}},
+		},
+		{
+			name: "Multiple spaces after semicolons",
+			signatures: []string{
+				`v=1;  a=rsa-sha256;  c=relaxed/relaxed;  d=example.com;  s=myselector;  bh=hash=;  b=sig==`,
+			},
+			expected: []DKIMHeader{{Domain: "example.com", Selector: "myselector"}},
+		},
+		{
+			name: "Ed25519 signature (RFC 8463)",
+			signatures: []string{
+				"v=1; a=ed25519-sha256; c=relaxed/relaxed;\r\n d=football.example.com; i=@football.example.com;\r\n q=dns/txt; s=brisbane; t=1528637909; h=from:to:subject;\r\n bh=2jUSOH9NhtVGCQWNr9BrIAPreKQjO6Sn7XIkfJVOzv8=;\r\n b=/gCrinpcQOoIfuHNQIbq4pgh9kyIK3AQ==",
+			},
+			expected: []DKIMHeader{{Domain: "football.example.com", Selector: "brisbane"}},
+		},
+		{
+			name: "Multiple signatures (ESP double-signing)",
+			signatures: []string{
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; d=mydomain.com; s=mail; h=from:to:subject; bh=hash1=; b=sig1==`,
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; d=sendib.com; s=mail; h=from:to:subject; bh=hash1=; b=sig2==`,
+			},
+			expected: []DKIMHeader{
+				{Domain: "mydomain.com", Selector: "mail"},
+				{Domain: "sendib.com", Selector: "mail"},
+			},
+		},
+		{
+			name: "Dual-algorithm signing (Ed25519 + RSA, same domain, different selectors)",
+			signatures: []string{
+				`v=1; a=ed25519-sha256; c=relaxed/relaxed; d=football.example.com; s=brisbane; h=from:to:subject; bh=hash=; b=edSig==`,
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; d=football.example.com; s=test; h=from:to:subject; bh=hash=; b=rsaSig==`,
+			},
+			expected: []DKIMHeader{
+				{Domain: "football.example.com", Selector: "brisbane"},
+				{Domain: "football.example.com", Selector: "test"},
+			},
+		},
+		{
+			name: "Amazon SES long selectors",
+			signatures: []string{
+				`v=1; a=rsa-sha256; c=relaxed/simple; d=amazonses.com; s=224i4yxa5dv7c2xz3womw6peuabd; h=from:to:subject; bh=sesHash=; b=sesSig==`,
+				`v=1; a=rsa-sha256; c=relaxed/simple; d=customerdomain.io; s=ug7nbtf4gccmlpwj322ax3p6ow6fovbt; h=from:to:subject; bh=sesHash=; b=customSig==`,
+			},
+			expected: []DKIMHeader{
+				{Domain: "amazonses.com", Selector: "224i4yxa5dv7c2xz3womw6peuabd"},
+				{Domain: "customerdomain.io", Selector: "ug7nbtf4gccmlpwj322ax3p6ow6fovbt"},
+			},
+		},
+		{
+			name: "Subdomain in d=",
+			signatures: []string{
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; d=mail.example.co.uk; s=dkim2025; h=from:to:subject; bh=hash=; b=sig==`,
+			},
+			expected: []DKIMHeader{{Domain: "mail.example.co.uk", Selector: "dkim2025"}},
+		},
+		{
+			name: "Deeply nested subdomain",
+			signatures: []string{
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; d=bounce.transactional.mail.example.com; s=s2048; h=from:to:subject; bh=hash=; b=sig==`,
+			},
+			expected: []DKIMHeader{{Domain: "bounce.transactional.mail.example.com", Selector: "s2048"}},
+		},
+		{
+			name: "Selector with hyphens (Microsoft 365 custom domain style)",
+			signatures: []string{
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; d=example.com; s=selector1-contoso-com; h=from:to:subject; bh=hash=; b=sig==`,
+			},
+			expected: []DKIMHeader{{Domain: "example.com", Selector: "selector1-contoso-com"}},
+		},
+		{
+			name: "Selector with dots",
+			signatures: []string{
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; d=example.com; s=smtp.mail; h=from:to:subject; bh=hash=; b=sig==`,
+			},
+			expected: []DKIMHeader{{Domain: "example.com", Selector: "smtp.mail"}},
+		},
+		{
+			name: "Single-character selector",
+			signatures: []string{
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; d=tiny.io; s=x; h=from:to:subject; bh=hash=; b=sig==`,
+			},
+			expected: []DKIMHeader{{Domain: "tiny.io", Selector: "x"}},
+		},
+		{
+			name: "Postmark-style timestamp selector, s= before d=",
+			signatures: []string{
+				`v=1; a=rsa-sha1; c=relaxed/relaxed; s=20130519032151pm; d=postmarkapp.com; h=From:Date:Subject; bh=vYFvy46eesUDGJ45hyBTH30JfN4=; b=iHeFQ+7rCiSQs3DPjR2eUSZSv4i==`,
+			},
+			expected: []DKIMHeader{{Domain: "postmarkapp.com", Selector: "20130519032151pm"}},
+		},
+		{
+			name: "d= and s= at the very end",
+			signatures: []string{
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; h=from:to:subject; bh=hash=; b=sig==; d=example.net; s=trailing`,
+			},
+			expected: []DKIMHeader{{Domain: "example.net", Selector: "trailing"}},
+		},
+		{
+			name: "Full tag set",
+			signatures: []string{
+				`v=1; a=rsa-sha256; d=example.com; s=selector1; c=relaxed/simple; q=dns/txt; i=user@example.com; t=1255993973; x=1256598773; h=From:Sender:Reply-To:Subject:Date:Message-Id:To:Cc; bh=+7qxGePcmmrtZAIVQAtkSSGHfQ/ftNuvUTWJ3vXC9Zc=; b=dB85+qM+If1KGQmqMLNpqLgNtUaG5dhGjYjQD6/QXtXmViJx8tf9gLEjcHr+musLCAvr0Fsn1DA3ZLLlUxpf4AR==`,
+			},
+			expected: []DKIMHeader{{Domain: "example.com", Selector: "selector1"}},
+		},
+		{
+			name: "Missing d= tag",
+			signatures: []string{
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; s=selector1; h=from:to; bh=hash=; b=sig==`,
+			},
+			expected: nil,
+		},
+		{
+			name: "Missing s= tag",
+			signatures: []string{
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; d=example.com; h=from:to; bh=hash=; b=sig==`,
+			},
+			expected: nil,
+		},
+		{
+			name: "Missing both d= and s= tags",
+			signatures: []string{
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; h=from:to; bh=hash=; b=sig==`,
+			},
+			expected: nil,
+		},
+		{
+			name: "Mix of valid and invalid signatures",
+			signatures: []string{
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; d=good.com; s=sel1; h=from:to; bh=hash=; b=sig==`,
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; s=orphan; h=from:to; bh=hash=; b=sig==`,
+				`v=1; a=rsa-sha256; c=relaxed/relaxed; d=also-good.com; s=sel2; h=from:to; bh=hash=; b=sig==`,
+			},
+			expected: []DKIMHeader{
+				{Domain: "good.com", Selector: "sel1"},
+				{Domain: "also-good.com", Selector: "sel2"},
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := parseDKIMSignatures(tt.signatures)
+			if len(result) != len(tt.expected) {
+				t.Fatalf("parseDKIMSignatures() returned %d results, want %d\n  got:  %+v\n  want: %+v", len(result), len(tt.expected), result, tt.expected)
+			}
+			for i := range tt.expected {
+				if result[i].Domain != tt.expected[i].Domain {
+					t.Errorf("result[%d].Domain = %q, want %q", i, result[i].Domain, tt.expected[i].Domain)
+				}
+				if result[i].Selector != tt.expected[i].Selector {
+					t.Errorf("result[%d].Selector = %q, want %q", i, result[i].Selector, tt.expected[i].Selector)
+				}
+			}
+		})
+	}
+}
+
 func TestValidateDKIM(t *testing.T) {
 	tests := []struct {
 		name     string

pkg/analyzer/parser.go

@@ -28,16 +28,9 @@ import (
 	"mime/multipart"
 	"net/mail"
 	"net/textproto"
-	"os"
 	"strings"
 )
 
-var hostname = ""
-
-func init() {
-	hostname, _ = os.Hostname()
-}
-
 // EmailMessage represents a parsed email message
 type EmailMessage struct {
 	Header     mail.Header
@@ -218,18 +211,18 @@ func buildRawHeaders(header mail.Header) string {
 }
 
 // GetAuthenticationResults extracts Authentication-Results headers
-// If hostname is provided, only returns headers that begin with that hostname
+// If receiverHostname is provided, only returns headers that begin with that hostname
-func (e *EmailMessage) GetAuthenticationResults() []string {
+func (e *EmailMessage) GetAuthenticationResults(receiverHostname string) []string {
 	allResults := e.Header[textproto.CanonicalMIMEHeaderKey("Authentication-Results")]
 
 	// If no hostname specified, return all results
-	if hostname == "" {
+	if receiverHostname == "" {
 		return allResults
 	}
 
 	// Filter results that begin with the specified hostname
 	var filtered []string
-	prefix := hostname + ";"
+	prefix := receiverHostname + ";"
 	for _, result := range allResults {
 		// Trim whitespace and check if it starts with hostname;
 		trimmed := strings.TrimSpace(result)

pkg/analyzer/parser_test.go

@@ -106,9 +106,6 @@ Content-Type: text/html; charset=utf-8
 }
 
 func TestGetAuthenticationResults(t *testing.T) {
-	// Force hostname
-	hostname = "example.com"
-
 	rawEmail := `From: sender@example.com
 To: recipient@example.com
 Subject: Test Email
@@ -123,7 +120,7 @@ Body content.
 		t.Fatalf("Failed to parse email: %v", err)
 	}
 
-	authResults := email.GetAuthenticationResults()
+	authResults := email.GetAuthenticationResults("example.com")
 	if len(authResults) != 2 {
 		t.Errorf("Expected 2 Authentication-Results headers, got: %d", len(authResults))
 	}

pkg/analyzer/report.go

@@ -43,6 +43,7 @@ type ReportGenerator struct {
 
 // NewReportGenerator creates a new report generator
 func NewReportGenerator(
+	receiverHostname string,
 	dnsTimeout time.Duration,
 	httpTimeout time.Duration,
 	rbls []string,
@@ -50,7 +51,7 @@ func NewReportGenerator(
 	checkAllIPs bool,
 ) *ReportGenerator {
 	return &ReportGenerator{
-		authAnalyzer:    NewAuthenticationAnalyzer(),
+		authAnalyzer:    NewAuthenticationAnalyzer(receiverHostname),
 		spamAnalyzer:    NewSpamAssassinAnalyzer(),
 		rspamdAnalyzer:  NewRspamdAnalyzer(),
 		dnsAnalyzer:     NewDNSAnalyzer(dnsTimeout),
@@ -83,7 +84,7 @@ func (r *ReportGenerator) AnalyzeEmail(email *EmailMessage) *AnalysisResults {
 	// Run all analyzers
 	results.Authentication = r.authAnalyzer.AnalyzeAuthentication(email)
 	results.Headers = r.headerAnalyzer.GenerateHeaderAnalysis(email, results.Authentication)
-	results.DNS = r.dnsAnalyzer.AnalyzeDNS(email, results.Authentication, results.Headers)
+	results.DNS = r.dnsAnalyzer.AnalyzeDNS(email, results.Headers)
 	results.RBL = r.rblChecker.CheckEmail(email)
 	results.DNSWL = r.dnswlChecker.CheckEmail(email)
 	results.SpamAssassin = r.spamAnalyzer.AnalyzeSpamAssassin(email)

pkg/analyzer/report_test.go

@@ -32,7 +32,7 @@ import (
 )
 
 func TestNewReportGenerator(t *testing.T) {
-	gen := NewReportGenerator(10*time.Second, 10*time.Second, DefaultRBLs, DefaultDNSWLs, false)
+	gen := NewReportGenerator("", 10*time.Second, 10*time.Second, DefaultRBLs, DefaultDNSWLs, false)
 	if gen == nil {
 		t.Fatal("Expected report generator, got nil")
 	}
@@ -55,7 +55,7 @@ func TestNewReportGenerator(t *testing.T) {
 }
 
 func TestAnalyzeEmail(t *testing.T) {
-	gen := NewReportGenerator(10*time.Second, 10*time.Second, DefaultRBLs, DefaultDNSWLs, false)
+	gen := NewReportGenerator("", 10*time.Second, 10*time.Second, DefaultRBLs, DefaultDNSWLs, false)
 
 	email := createTestEmail()
 
@@ -75,7 +75,7 @@ func TestAnalyzeEmail(t *testing.T) {
 }
 
 func TestGenerateReport(t *testing.T) {
-	gen := NewReportGenerator(10*time.Second, 10*time.Second, DefaultRBLs, DefaultDNSWLs, false)
+	gen := NewReportGenerator("", 10*time.Second, 10*time.Second, DefaultRBLs, DefaultDNSWLs, false)
 	testID := uuid.New()
 
 	email := createTestEmail()
@@ -130,7 +130,7 @@ func TestGenerateReport(t *testing.T) {
 }
 
 func TestGenerateReportWithSpamAssassin(t *testing.T) {
-	gen := NewReportGenerator(10*time.Second, 10*time.Second, DefaultRBLs, DefaultDNSWLs, false)
+	gen := NewReportGenerator("", 10*time.Second, 10*time.Second, DefaultRBLs, DefaultDNSWLs, false)
 	testID := uuid.New()
 
 	email := createTestEmailWithSpamAssassin()
@@ -150,7 +150,7 @@ func TestGenerateReportWithSpamAssassin(t *testing.T) {
 }
 
 func TestGenerateRawEmail(t *testing.T) {
-	gen := NewReportGenerator(10*time.Second, 10*time.Second, DefaultRBLs, DefaultDNSWLs, false)
+	gen := NewReportGenerator("", 10*time.Second, 10*time.Second, DefaultRBLs, DefaultDNSWLs, false)
 
 	tests := []struct {
 		name     string

pkg/analyzer/rspamd.go

@@ -51,6 +51,13 @@ func (a *RspamdAnalyzer) AnalyzeRspamd(email *EmailMessage) *api.RspamdResult {
 		return nil
 	}
 
+	// Require at least X-Spamd-Result or X-Rspamd-Score to produce a meaningful report
+	_, hasSpamdResult := headers["X-Spamd-Result"]
+	_, hasRspamdScore := headers["X-Rspamd-Score"]
+	if !hasSpamdResult && !hasRspamdScore {
+		return nil
+	}
+
 	result := &api.RspamdResult{
 		Symbols: make(map[string]api.RspamdSymbol),
 	}

pkg/analyzer/spamassassin.go

@@ -45,6 +45,14 @@ func (a *SpamAssassinAnalyzer) AnalyzeSpamAssassin(email *EmailMessage) *api.Spa
 		return nil
 	}
 
+	// Require at least X-Spam-Status, X-Spam-Score, or X-Spam-Flag to produce a meaningful report
+	_, hasStatus := headers["X-Spam-Status"]
+	_, hasScore := headers["X-Spam-Score"]
+	_, hasFlag := headers["X-Spam-Flag"]
+	if !hasStatus && !hasScore && !hasFlag {
+		return nil
+	}
+
 	result := &api.SpamAssassinResult{
 		TestDetails: make(map[string]api.SpamTestDetail),
 	}

web/src/lib/components/AuthenticationCard.svelte

@@ -13,6 +13,12 @@
 
     let { authentication, authenticationGrade, authenticationScore, dnsResults }: Props = $props();
 
+    let allRequiredMissing = $derived(
+        !authentication.spf &&
+            (!authentication.dkim || authentication.dkim.length === 0) &&
+            !authentication.dmarc,
+    );
+
     function getAuthResultClass(result: string, noneIsFail: boolean): string {
         switch (result) {
             case "pass":
@@ -97,6 +103,28 @@
             </span>
         </h4>
     </div>
+    {#if allRequiredMissing}
+        <div class="card-body border-bottom">
+            <div class="alert alert-warning mb-0">
+                <i class="bi bi-exclamation-triangle-fill me-2"></i>
+                <strong>No authentication results found.</strong>
+                <p class="mb-0 mt-1">
+                    This usually means either:
+                </p>
+                <ul class="mb-0 mt-1">
+                    <li>
+                        The receiving mail server is not configured to verify email authentication
+                        (no <code>Authentication-Results</code> header was found in the message).
+                    </li>
+                    <li>
+                        The <code>Authentication-Results</code> header exists but the receiver
+                        hostname does not match the configured
+                        <code>--receiver-hostname</code> value.
+                    </li>
+                </ul>
+            </div>
+        </div>
+    {/if}
     <div class="list-group list-group-flush">
         <!-- IPREV -->
         {#if authentication.iprev}

web/src/lib/components/SummaryCard.svelte

@@ -25,16 +25,32 @@
 
         // Email sender information
         const mailFrom = report.header_analysis?.headers?.from?.value || "an unknown sender";
-        const hasDkim = report.authentication?.dkim && report.authentication?.dkim.length > 0;
+        const hasDkim =
-        const dkimPassed = hasDkim && report.authentication?.dkim?.some((d) => d.result === "pass");
+            report.dns_results?.dkim_records && report.dns_results?.dkim_records?.length > 0;
+        const dkimPassed =
+            report.authentication?.dkim &&
+            report.authentication?.dkim.length > 0 &&
+            report.authentication?.dkim?.some((d) => d.result === "pass");
 
         segments.push({ text: "Received a " });
         segments.push({
-            text: dkimPassed ? "DKIM-signed" : "non-DKIM-signed",
+            text: hasDkim ? "DKIM-signed" : "non-DKIM-signed",
-            highlight: { color: dkimPassed ? "good" : "danger", bold: true },
+            highlight: {
-            link: "#authentication-dkim",
+                color: hasDkim ? (dkimPassed ? "good" : "warning") : "danger",
+                bold: true,
+            },
+            link: hasDkim && dkimPassed ? "#authentication-dkim" : "#dns-details",
         });
-        segments.push({ text: " email from " });
+        segments.push({ text: " email" });
+        if (hasDkim && !dkimPassed) {
+            segments.push({ text: " with " });
+            segments.push({
+                text: "an invalid signature",
+                highlight: { color: "danger", bold: true },
+                link: "#authentication-dkim",
+            });
+        }
+        segments.push({ text: " from " });
         segments.push({
             text: mailFrom,
             highlight: { emphasis: true },