git » chasquid » commit c2d0d5f

diff --git a/internal/smtpsrv/conn.go b/internal/smtpsrv/conn.go
index 592091f..1031c61 100644
--- a/internal/smtpsrv/conn.go
+++ b/internal/smtpsrv/conn.go
@@ -298,6 +298,9 @@ func (c *Conn) MAIL(params string) (code int, msg string) {
 	if !strings.HasPrefix(strings.ToLower(params), "from:") {
 		return 500, "unknown command"
 	}
+	if c.mode == ModeSubmission && !c.completedAuth {
+		return 550, "mail to submission port must be authenticated"
+	}
 
 	rawAddr := ""
 	_, err := fmt.Sscanf(params[5:], "%s ", &rawAddr)
diff --git a/internal/smtpsrv/server_test.go b/internal/smtpsrv/server_test.go
index e7969c2..51f9286 100644
--- a/internal/smtpsrv/server_test.go
+++ b/internal/smtpsrv/server_test.go
@@ -146,6 +146,15 @@ func TestAuth(t *testing.T) {
 	sendEmailWithAuth(t, c, auth)
 }
 
+func TestSubmissionWithoutAuth(t *testing.T) {
+	c := mustDial(t, ModeSubmission, true)
+	defer c.Close()
+
+	if err := c.Mail("from@from"); err == nil {
+		t.Errorf("Mail not failed as expected")
+	}
+}
+
 func TestAuthOnSMTP(t *testing.T) {
 	c := mustDial(t, ModeSMTP, true)
 	defer c.Close()