diff --git a/message/part.go b/message/part.go
index 21b3f474f..4d158d737 100644
--- a/message/part.go
+++ b/message/part.go
@@ -33,6 +33,7 @@ var Pedantic bool
 
 var (
 	ErrBadContentType = errors.New("bad content-type")
+	ErrHeader         = errors.New("bad message header")
 )
 
 var (
@@ -394,6 +395,8 @@ func newPart(log mlog.Log, strict bool, r io.ReaderAt, offset int64, parent *Par
 }
 
 // Header returns the parsed header of this part.
+//
+// Returns a ErrHeader for messages with invalid header syntax.
 func (p *Part) Header() (textproto.MIMEHeader, error) {
 	if p.header != nil {
 		return p.header, nil
@@ -431,6 +434,12 @@ func parseHeader(r io.Reader) (textproto.MIMEHeader, error) {
 	}
 	msg, err := mail.ReadMessage(bytes.NewReader(buf))
 	if err != nil {
+		// Recognize parsing errors from net/mail.ReadMessage.
+		// todo: replace with own message parsing code that returns proper error types.
+		errstr := err.Error()
+		if strings.HasPrefix(errstr, "malformed initial line:") || strings.HasPrefix(errstr, "malformed header line:") {
+			err = fmt.Errorf("%w: %v", ErrHeader, err)
+		}
 		return zero, err
 	}
 	return textproto.MIMEHeader(msg.Header), nil
diff --git a/webmail/message.go b/webmail/message.go
index 9237624c7..74d609f11 100644
--- a/webmail/message.go
+++ b/webmail/message.go
@@ -232,7 +232,7 @@ func parsedMessage(log mlog.Log, m store.Message, state *msgState, full, msgitem
 	if full && state.part.BodyOffset > 0 {
 		hdrs, err := state.part.Header()
 		if err != nil {
-			return ParsedMessage{}, fmt.Errorf("parsing headers: %v", err)
+			return ParsedMessage{}, fmt.Errorf("parsing headers: %w", err)
 		}
 		pm.Headers = hdrs
 
diff --git a/webmail/view.go b/webmail/view.go
index 9a6598c22..46276c644 100644
--- a/webmail/view.go
+++ b/webmail/view.go
@@ -1486,16 +1486,19 @@ func queryMessages(ctx context.Context, log mlog.Log, acc *store.Account, tx *bs
 
 		var pm *ParsedMessage
 		if m.ID == page.DestMessageID || page.DestMessageID == 0 && have == 0 && page.AnchorMessageID == 0 {
-			// For threads, if there was not DestMessageID, we may be getting the newest
+			// For threads, if there was no DestMessageID, we may be getting the newest
 			// message. For an initial view, this isn't necessarily the first the user is
 			// expected to read first, that would be the first unread, which we'll get below
 			// when gathering the thread.
 			found = true
 			xpm, err := parsedMessage(log, m, &state, true, false)
-			if err != nil {
+			if err != nil && errors.Is(err, message.ErrHeader) {
+				log.Debug("not returning parsed message due to invalid headers", slog.Int64("msgid", m.ID), slog.Any("err", err))
+			} else if err != nil {
 				return fmt.Errorf("parsing message %d: %v", m.ID, err)
+			} else {
+				pm = &xpm
 			}
-			pm = &xpm
 		}
 
 		mi, err := messageItem(log, m, &state)
@@ -1613,10 +1616,13 @@ func gatherThread(log mlog.Log, tx *bstore.Tx, acc *store.Account, v view, m sto
 			if tm.ID == destMessageID || destMessageID == 0 && first && (pm == nil || !firstUnread && !tm.Seen) {
 				firstUnread = !tm.Seen
 				xpm, err := parsedMessage(log, tm, &xstate, true, false)
-				if err != nil {
+				if err != nil && errors.Is(err, message.ErrHeader) {
+					log.Debug("not returning parsed message due to invalid headers", slog.Int64("msgid", m.ID), slog.Any("err", err))
+				} else if err != nil {
 					return fmt.Errorf("parsing thread message %d: %v", tm.ID, err)
+				} else {
+					pm = &xpm
 				}
-				pm = &xpm
 			}
 			return nil
 		}()
@@ -1631,10 +1637,13 @@ func gatherThread(log mlog.Log, tx *bstore.Tx, acc *store.Account, v view, m sto
 		xstate := msgState{acc: acc}
 		defer xstate.clear()
 		xpm, err := parsedMessage(log, m, &xstate, true, false)
-		if err != nil {
+		if err != nil && errors.Is(err, message.ErrHeader) {
+			log.Debug("not returning parsed message due to invalid headers", slog.Int64("msgid", m.ID), slog.Any("err", err))
+		} else if err != nil {
 			return nil, nil, fmt.Errorf("parsing thread message %d: %v", m.ID, err)
+		} else {
+			pm = &xpm
 		}
-		pm = &xpm
 	}
 
 	return mil, pm, nil