diff --git a/internal/smtpserver/session_local.go b/internal/smtpserver/session_local.go
index 5559498..0282b72 100644
--- a/internal/smtpserver/session_local.go
+++ b/internal/smtpserver/session_local.go
@@ -61,6 +61,11 @@ func (s *SessionLocal) Data(r io.Reader) error {
 			time.Now().String(),
 		),
 	)
+	if !m.Header.Has("Date") {
+		m.Header.Add(
+			"Date", time.Now().UTC().Format(time.RFC822),
+		)
+	}
 
 	var b bytes.Buffer
 	if err := m.WriteTo(&b); err != nil {
diff --git a/internal/smtpserver/session_remote.go b/internal/smtpserver/session_remote.go
index dcac8e8..26ee340 100644
--- a/internal/smtpserver/session_remote.go
+++ b/internal/smtpserver/session_remote.go
@@ -67,6 +67,9 @@ func (s *SessionRemote) Data(r io.Reader) error {
 			time.Now().String(),
 		),
 	)
+	m.Header.Add(
+		"Delivery-Date", time.Now().UTC().Format(time.RFC822),
+	)
 
 	var b bytes.Buffer
 	if err := m.WriteTo(&b); err != nil {