fix: update Message-ID determination logic to prefer IMAP-parsed IDs over raw headers

internal/inbox/channel/email/imap.go

@@ -140,6 +140,7 @@ func (e *Email) fetchAndProcessMessages(ctx context.Context, client *imapclient.
 					headerAutoSubmitted,
 					headerAutoreply,
 					headerLibredeskLoopPrevention,
+					headerMessageID,
 				},
 			},
 		},
@@ -151,6 +152,7 @@ func (e *Email) fetchAndProcessMessages(ctx context.Context, client *imapclient.
 		seqNum             uint32
 		autoReply          bool
 		isLoop             bool
+		extractedMessageID string
 	}
 	var messages []msgData
 
@@ -185,6 +187,7 @@ func (e *Email) fetchAndProcessMessages(ctx context.Context, client *imapclient.
 			env                *imap.Envelope
 			autoReply          bool
 			isLoop             bool
+			extractedMessageID string
 		)
 		// Process all fetch items for the current message.
 		for {
@@ -215,6 +218,9 @@ func (e *Email) fetchAndProcessMessages(ctx context.Context, client *imapclient.
 				if isLoopMessage(envelope, inboxEmail) {
 					isLoop = true
 				}
+
+				// Extract Message-Id from raw headers as fallback for problematic Message IDs
+				extractedMessageID = extractMessageIDFromHeaders(envelope)
 			}
 
 			// Envelope.
@@ -223,12 +229,13 @@ func (e *Email) fetchAndProcessMessages(ctx context.Context, client *imapclient.
 			}
 		}
 
-		// Skip if we couldn't get headers or envelope.
+		// Skip if we couldn't get the envelope.
 		if env == nil {
+			e.lo.Warn("skipping message without envelope", "seq_num", msg.SeqNum, "inbox_id", e.Identifier())
 			continue
 		}
 
-		messages = append(messages, msgData{env: env, seqNum: msg.SeqNum, autoReply: autoReply, isLoop: isLoop})
+		messages = append(messages, msgData{env: env, seqNum: msg.SeqNum, autoReply: autoReply, isLoop: isLoop, extractedMessageID: extractedMessageID})
 	}
 
 	// Now process each collected message.
@@ -253,7 +260,7 @@ func (e *Email) fetchAndProcessMessages(ctx context.Context, client *imapclient.
 		}
 
 		// Process the envelope.
-		if err := e.processEnvelope(ctx, client, msgData.env, msgData.seqNum, inboxID); err != nil && err != context.Canceled {
+		if err := e.processEnvelope(ctx, client, msgData.env, msgData.seqNum, inboxID, msgData.extractedMessageID); err != nil && err != context.Canceled {
 			e.lo.Error("error processing envelope", "error", err)
 		}
 	}
@@ -262,17 +269,32 @@ func (e *Email) fetchAndProcessMessages(ctx context.Context, client *imapclient.
 }
 
 // processEnvelope processes a single email envelope.
-func (e *Email) processEnvelope(ctx context.Context, client *imapclient.Client, env *imap.Envelope, seqNum uint32, inboxID int) error {
+func (e *Email) processEnvelope(ctx context.Context, client *imapclient.Client, env *imap.Envelope, seqNum uint32, inboxID int, extractedMessageID string) error {
 	if len(env.From) == 0 {
 		e.lo.Warn("no sender received for email", "message_id", env.MessageID)
 		return nil
 	}
 	var fromAddress = strings.ToLower(env.From[0].Addr())
 
+	// Determine final Message ID - prefer IMAP-parsed, fallback to raw header extraction
+	messageID := env.MessageID
+	if messageID == "" {
+		messageID = extractedMessageID
+		if messageID != "" {
+			e.lo.Debug("using raw header Message-ID as fallback for malformed ID", "message_id", messageID, "subject", env.Subject, "from", fromAddress)
+		}
+	}
+
+	// Drop message if we still don't have a valid Message ID
+	if messageID == "" {
+		e.lo.Error("dropping message: no valid Message-ID found in IMAP parsing or raw headers", "subject", env.Subject, "from", fromAddress)
+		return nil
+	}
+
 	// Check if the message already exists in the database; if it does, ignore it.
-	exists, err := e.messageStore.MessageExists(env.MessageID)
+	exists, err := e.messageStore.MessageExists(messageID)
 	if err != nil {
-		e.lo.Error("error checking if message exists", "message_id", env.MessageID)
+		e.lo.Error("error checking if message exists", "message_id", messageID)
 		return fmt.Errorf("checking if message exists in DB: %w", err)
 	}
 	if exists {
@@ -291,7 +313,7 @@ func (e *Email) processEnvelope(ctx context.Context, client *imapclient.Client,
 		return nil
 	}
 
-	e.lo.Debug("processing new incoming message", "message_id", env.MessageID, "subject", env.Subject, "from", fromAddress, "inbox_id", inboxID)
+	e.lo.Debug("processing new incoming message", "message_id", messageID, "subject", env.Subject, "from", fromAddress, "inbox_id", inboxID)
 
 	// Make contact.
 	firstName, lastName := getContactName(env.From[0])
@@ -350,7 +372,7 @@ func (e *Email) processEnvelope(ctx context.Context, client *imapclient.Client,
 			InboxID:    inboxID,
 			Status:     models.MessageStatusReceived,
 			Subject:    env.Subject,
-			SourceID:   null.StringFrom(env.MessageID),
+			SourceID:   null.StringFrom(messageID),
 			Meta:       meta,
 		},
 		Contact: contact,
@@ -385,7 +407,7 @@ func (e *Email) processEnvelope(ctx context.Context, client *imapclient.Client,
 		}
 
 		if fullItem, ok := fullFetchItem.(imapclient.FetchItemDataBodySection); ok {
-			e.lo.Debug("fetching full message body", "message_id", env.MessageID)
+			e.lo.Debug("fetching full message body", "message_id", messageID)
 			return e.processFullMessage(fullItem, incomingMsg)
 		}
 	}
@@ -534,3 +556,13 @@ func extractAllHTMLParts(part *enmime.Part) []string {
 
 	return htmlParts
 }
+
+// extractMessageIDFromHeaders extracts and cleans the Message-ID from email headers.
+// This function handles problematic Message IDs by extracting them from raw headers
+// and cleaning them of angle brackets and whitespace.
+func extractMessageIDFromHeaders(envelope *enmime.Envelope) string {
+	if rawMessageID := envelope.GetHeader(headerMessageID); rawMessageID != "" {
+		return strings.TrimSpace(strings.Trim(rawMessageID, "<>"))
+	}
+	return ""
+}

internal/inbox/channel/email/imap_test.go

@@ -0,0 +1,123 @@
+package email
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/emersion/go-message/mail"
+	"github.com/jhillyerd/enmime"
+)
+
+
+// TestGoIMAPMessageIDParsing shows how go-imap fails to parse malformed Message-IDs
+// and demonstrates the fallback solution.
+// go-imap uses mail.Header.MessageID() which strictly follows RFC 5322 and returns
+// empty strings for Message-IDs with multiple @ symbols.
+//
+// This caused emails to be dropped since we require Message-IDs for deduplication.
+// References:
+// - https://community.mailcow.email/d/701-multiple-at-in-message-id/5
+// - https://github.com/emersion/go-message/issues/154#issuecomment-1425634946
+func TestGoIMAPMessageIDParsing(t *testing.T) {
+	testCases := []struct {
+		input            string
+		expectedIMAP     string
+		expectedFallback string
+		name             string
+	}{
+		{"<normal@example.com>", "normal@example.com", "normal@example.com", "normal message ID"},
+		{"<malformed@@example.com>", "", "malformed@@example.com", "double @ - IMAP fails, fallback works"},
+		{"<001c01d710db$a8137a50$f83a6ef0$@jones.smith@example.com>", "", "001c01d710db$a8137a50$f83a6ef0$@jones.smith@example.com", "mailcow-style - IMAP fails, fallback works"},
+		{"<test@@@domain.com>", "", "test@@@domain.com", "triple @ - IMAP fails, fallback works"},
+		{"  <abc123@example.com>  ", "abc123@example.com", "abc123@example.com", "with whitespace - both handle correctly"},
+		{"abc123@example.com", "", "abc123@example.com", "no angle brackets - IMAP fails, fallback works"},
+		{"", "", "", "empty input"},
+		{"<>", "", "", "empty brackets"},
+		{"<CAFnQjQFhY8z@mail.example.com@gateway.company.com>", "", "CAFnQjQFhY8z@mail.example.com@gateway.company.com", "gateway-style - IMAP fails, fallback works"},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			// Test go-imap parsing behavior
+			var h mail.Header
+			h.Set("Message-Id", tc.input)
+			imapResult, _ := h.MessageID()
+
+			if imapResult != tc.expectedIMAP {
+				t.Errorf("IMAP parsing of %q: expected %q, got %q", tc.input, tc.expectedIMAP, imapResult)
+			}
+
+			// Test fallback solution
+			if tc.input != "" {
+				rawEmail := "From: test@example.com\nMessage-ID: " + tc.input + "\n\nBody"
+				envelope, err := enmime.ReadEnvelope(strings.NewReader(rawEmail))
+				if err != nil {
+					t.Fatal(err)
+				}
+
+				fallbackResult := extractMessageIDFromHeaders(envelope)
+				if fallbackResult != tc.expectedFallback {
+					t.Errorf("Fallback extraction of %q: expected %q, got %q", tc.input, tc.expectedFallback, fallbackResult)
+				}
+
+				// Critical check: ensure fallback works when IMAP fails
+				if imapResult == "" && tc.expectedFallback != "" && fallbackResult == "" {
+					t.Errorf("CRITICAL: Both IMAP and fallback failed for %q - would drop email!", tc.input)
+				}
+			}
+		})
+	}
+}
+
+
+// TestEdgeCasesMessageID tests additional edge cases for Message-ID extraction.
+func TestEdgeCasesMessageID(t *testing.T) {
+	tests := []struct {
+		name     string
+		email    string
+		expected string
+	}{
+		{
+			name: "no Message-ID header",
+			email: `From: test@example.com
+To: inbox@test.com
+Subject: Test
+
+Body`,
+			expected: "",
+		},
+		{
+			name: "malformed header syntax",
+			email: `From: test@example.com
+Message-ID: malformed-no-brackets@@domain.com
+To: inbox@test.com
+
+Body`,
+			expected: "malformed-no-brackets@@domain.com",
+		},
+		{
+			name: "multiple Message-ID headers (first wins)",
+			email: `From: test@example.com
+Message-ID: <first@example.com>
+Message-ID: <second@@example.com>
+To: inbox@test.com
+
+Body`,
+			expected: "first@example.com",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			envelope, err := enmime.ReadEnvelope(strings.NewReader(tt.email))
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			result := extractMessageIDFromHeaders(envelope)
+			if result != tt.expected {
+				t.Errorf("Expected %q, got %q", tt.expected, result)
+			}
+		})
+	}
+}