Add rspamd as a second spam filter alongside SpamAssassin

Closes: #36

pkg/analyzer/parser.go

@@ -264,6 +264,26 @@ func (e *EmailMessage) GetSpamAssassinHeaders() map[string]string {
 	return headers
 }
 
+// GetRspamdHeaders extracts rspamd-related headers
+func (e *EmailMessage) GetRspamdHeaders() map[string]string {
+	headers := make(map[string]string)
+
+	rspamdHeaders := []string{
+		"X-Spamd-Result",
+		"X-Rspamd-Score",
+		"X-Rspamd-Action",
+		"X-Rspamd-Server",
+	}
+
+	for _, headerName := range rspamdHeaders {
+		if value := e.Header.Get(headerName); value != "" {
+			headers[headerName] = value
+		}
+	}
+
+	return headers
+}
+
 // GetTextParts returns all text/plain parts
 func (e *EmailMessage) GetTextParts() []MessagePart {
 	return filterParts(e.Parts, func(p MessagePart) bool {

pkg/analyzer/report.go

@@ -33,6 +33,7 @@ import (
 type ReportGenerator struct {
 	authAnalyzer    *AuthenticationAnalyzer
 	spamAnalyzer    *SpamAssassinAnalyzer
+	rspamdAnalyzer  *RspamdAnalyzer
 	dnsAnalyzer     *DNSAnalyzer
 	rblChecker      *RBLChecker
 	contentAnalyzer *ContentAnalyzer
@@ -49,6 +50,7 @@ func NewReportGenerator(
 	return &ReportGenerator{
 		authAnalyzer:    NewAuthenticationAnalyzer(),
 		spamAnalyzer:    NewSpamAssassinAnalyzer(),
+		rspamdAnalyzer:  NewRspamdAnalyzer(),
 		dnsAnalyzer:     NewDNSAnalyzer(dnsTimeout),
 		rblChecker:      NewRBLChecker(dnsTimeout, rbls, checkAllIPs),
 		contentAnalyzer: NewContentAnalyzer(httpTimeout),
@@ -65,6 +67,7 @@ type AnalysisResults struct {
 	Headers        *api.HeaderAnalysis
 	RBL            *RBLResults
 	SpamAssassin   *api.SpamAssassinResult
+	Rspamd         *api.RspamdResult
 }
 
 // AnalyzeEmail performs complete email analysis
@@ -79,6 +82,7 @@ func (r *ReportGenerator) AnalyzeEmail(email *EmailMessage) *AnalysisResults {
 	results.DNS = r.dnsAnalyzer.AnalyzeDNS(email, results.Authentication, results.Headers)
 	results.RBL = r.rblChecker.CheckEmail(email)
 	results.SpamAssassin = r.spamAnalyzer.AnalyzeSpamAssassin(email)
+	results.Rspamd = r.rspamdAnalyzer.AnalyzeRspamd(email)
 	results.Content = r.contentAnalyzer.AnalyzeContent(email)
 
 	return results
@@ -134,10 +138,26 @@ func (r *ReportGenerator) GenerateReport(testID uuid.UUID, results *AnalysisResu
 		blacklistScore, blacklistGrade = r.rblChecker.CalculateRBLScore(results.RBL)
 	}
 
-	spamScore := 0
+	saScore, saGrade := r.spamAnalyzer.CalculateSpamAssassinScore(results.SpamAssassin)
+	rspamdScore, rspamdGrade := r.rspamdAnalyzer.CalculateRspamdScore(results.Rspamd)
+
+	// Combine SpamAssassin and rspamd scores 50/50.
+	// If only one filter ran (the other returns "" grade), use that filter's score alone.
+	var spamScore int
 	var spamGrade string
-	if results.SpamAssassin != nil {
-		spamScore, spamGrade = r.spamAnalyzer.CalculateSpamAssassinScore(results.SpamAssassin)
+	switch {
+	case saGrade == "" && rspamdGrade == "":
+		spamScore = 0
+		spamGrade = ""
+	case saGrade == "":
+		spamScore = rspamdScore
+		spamGrade = rspamdGrade
+	case rspamdGrade == "":
+		spamScore = saScore
+		spamGrade = saGrade
+	default:
+		spamScore = (saScore + rspamdScore) / 2
+		spamGrade = MinGrade(saGrade, rspamdGrade)
 	}
 
 	report.Summary = &api.ScoreSummary{
@@ -177,9 +197,22 @@ func (r *ReportGenerator) GenerateReport(testID uuid.UUID, results *AnalysisResu
 		report.Blacklists = &results.RBL.Checks
 	}
 
-	// Add SpamAssassin result
+	// Add SpamAssassin result with individual deliverability score
+	if results.SpamAssassin != nil {
+		saGradeTyped := api.SpamAssassinResultDeliverabilityGrade(saGrade)
+		results.SpamAssassin.DeliverabilityScore = api.PtrTo(saScore)
+		results.SpamAssassin.DeliverabilityGrade = &saGradeTyped
+	}
 	report.Spamassassin = results.SpamAssassin
 
+	// Add rspamd result with individual deliverability score
+	if results.Rspamd != nil {
+		rspamdGradeTyped := api.RspamdResultDeliverabilityGrade(rspamdGrade)
+		results.Rspamd.DeliverabilityScore = api.PtrTo(rspamdScore)
+		results.Rspamd.DeliverabilityGrade = &rspamdGradeTyped
+	}
+	report.Rspamd = results.Rspamd
+
 	// Add raw headers
 	if results.Email != nil && results.Email.RawHeaders != "" {
 		report.RawHeaders = &results.Email.RawHeaders

pkg/analyzer/rspamd.go

@@ -0,0 +1,152 @@
+// This file is part of the happyDeliver (R) project.
+// Copyright (c) 2026 happyDomain
+// Authors: Pierre-Olivier Mercier, et al.
+//
+// This program is offered under a commercial and under the AGPL license.
+// For commercial licensing, contact us at <contact@happydomain.org>.
+//
+// For AGPL licensing:
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package analyzer
+
+import (
+	"math"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"git.happydns.org/happyDeliver/internal/api"
+)
+
+// Default rspamd action thresholds (rspamd built-in defaults)
+const (
+	rspamdDefaultRejectThreshold    float32 = 15
+	rspamdDefaultAddHeaderThreshold float32 = 6
+)
+
+// RspamdAnalyzer analyzes rspamd results from email headers
+type RspamdAnalyzer struct{}
+
+// NewRspamdAnalyzer creates a new rspamd analyzer
+func NewRspamdAnalyzer() *RspamdAnalyzer {
+	return &RspamdAnalyzer{}
+}
+
+// AnalyzeRspamd extracts and analyzes rspamd results from email headers
+func (a *RspamdAnalyzer) AnalyzeRspamd(email *EmailMessage) *api.RspamdResult {
+	headers := email.GetRspamdHeaders()
+	if len(headers) == 0 {
+		return nil
+	}
+
+	result := &api.RspamdResult{
+		Symbols: make(map[string]api.RspamdSymbol),
+	}
+
+	// Parse X-Spamd-Result header (primary source for score, threshold, and symbols)
+	// Format: "default: False [-3.91 / 15.00];\n\tSYMBOL(score)[params]; ..."
+	if spamdResult, ok := headers["X-Spamd-Result"]; ok {
+		a.parseSpamdResult(spamdResult, result)
+	}
+
+	// Parse X-Rspamd-Score as override/fallback for score
+	if scoreHeader, ok := headers["X-Rspamd-Score"]; ok {
+		if score, err := strconv.ParseFloat(strings.TrimSpace(scoreHeader), 64); err == nil {
+			result.Score = float32(score)
+		}
+	}
+
+	// Parse X-Rspamd-Server
+	if serverHeader, ok := headers["X-Rspamd-Server"]; ok {
+		server := strings.TrimSpace(serverHeader)
+		result.Server = &server
+	}
+
+	// Derive IsSpam from score vs reject threshold.
+	if result.Threshold > 0 {
+		result.IsSpam = result.Score >= result.Threshold
+	} else {
+		result.IsSpam = result.Score >= rspamdDefaultAddHeaderThreshold
+	}
+
+	return result
+}
+
+// parseSpamdResult parses the X-Spamd-Result header
+// Format: "default: False [-3.91 / 15.00];\n\tSYMBOL(score)[params]; ..."
+func (a *RspamdAnalyzer) parseSpamdResult(header string, result *api.RspamdResult) {
+	// Extract score and threshold from the first line
+	// e.g. "default: False [-3.91 / 15.00]"
+	scoreRe := regexp.MustCompile(`\[\s*(-?\d+\.?\d*)\s*/\s*(-?\d+\.?\d*)\s*\]`)
+	if matches := scoreRe.FindStringSubmatch(header); len(matches) > 2 {
+		if score, err := strconv.ParseFloat(matches[1], 64); err == nil {
+			result.Score = float32(score)
+		}
+		if threshold, err := strconv.ParseFloat(matches[2], 64); err == nil {
+			result.Threshold = float32(threshold)
+
+			// No threshold? use default AddHeaderThreshold
+			if result.Threshold <= 0 {
+				result.Threshold = rspamdDefaultAddHeaderThreshold
+			}
+		}
+	}
+
+	// Parse is_spam from header (before we may get action from X-Rspamd-Action)
+	firstLine := strings.SplitN(header, ";", 2)[0]
+	if strings.Contains(firstLine, ": True") || strings.Contains(firstLine, ": true") {
+		result.IsSpam = true
+	}
+
+	// Parse symbols: SYMBOL(score)[params]
+	// Each symbol entry is separated by ";"
+	symbolRe := regexp.MustCompile(`(\w+)\((-?\d+\.?\d*)\)(?:\[([^\]]*)\])?`)
+	for _, part := range strings.Split(header, ";") {
+		part = strings.TrimSpace(part)
+		matches := symbolRe.FindStringSubmatch(part)
+		if len(matches) > 2 {
+			name := matches[1]
+			score, _ := strconv.ParseFloat(matches[2], 64)
+			sym := api.RspamdSymbol{
+				Name:  name,
+				Score: float32(score),
+			}
+			if len(matches) > 3 && matches[3] != "" {
+				params := matches[3]
+				sym.Params = &params
+			}
+			result.Symbols[name] = sym
+		}
+	}
+}
+
+// CalculateRspamdScore calculates the rspamd contribution to deliverability (0-100 scale)
+func (a *RspamdAnalyzer) CalculateRspamdScore(result *api.RspamdResult) (int, string) {
+	if result == nil {
+		return 100, "" // rspamd not installed
+	}
+
+	threshold := result.Threshold
+	percentage := 100 - int(math.Round(float64(result.Score*100/(2*threshold))))
+
+	if percentage > 100 {
+		return 100, "A+"
+	} else if percentage < 0 {
+		return 0, "F"
+	}
+
+	// Linear scale between 0 and threshold
+	return percentage, ScoreToGrade(percentage)
+}

pkg/analyzer/scoring.go

@@ -69,3 +69,31 @@ func ScoreToGradeKind(score int) string {
 func ScoreToReportGrade(score int) api.ReportGrade {
 	return api.ReportGrade(ScoreToGrade(score))
 }
+
+// gradeRank returns a numeric rank for a grade (lower = worse)
+func gradeRank(grade string) int {
+	switch grade {
+	case "A+":
+		return 6
+	case "A":
+		return 5
+	case "B":
+		return 4
+	case "C":
+		return 3
+	case "D":
+		return 2
+	case "E":
+		return 1
+	default:
+		return 0
+	}
+}
+
+// MinGrade returns the minimal (worse) grade between the two given grades
+func MinGrade(a, b string) string {
+	if gradeRank(a) <= gradeRank(b) {
+		return a
+	}
+	return b
+}

pkg/analyzer/spamassassin.go

@@ -195,7 +195,7 @@ func (a *SpamAssassinAnalyzer) parseSpamReport(report string, result *api.SpamAs
 // CalculateSpamAssassinScore calculates the SpamAssassin contribution to deliverability
 func (a *SpamAssassinAnalyzer) CalculateSpamAssassinScore(result *api.SpamAssassinResult) (int, string) {
 	if result == nil {
-		return 100, "" // No spam scan results, assume good
+		return 100, "" // No spam scan results
 	}
 
 	// SpamAssassin score typically ranges from -10 to +20