if local part is just postmaster, String() returns postmaster #199

mail/envelope.go

@@ -58,6 +58,9 @@ func (a *Address) String() string {
 	if a.IsEmpty() {
 		return ""
 	}
+	if a.User == "postmaster" && a.Host == "" {
+		return "postmaster"
+	}
 	if a.Quoted {
 		var sb bytes.Buffer
 		sb.WriteByte('"')

mail/envelope_test.go

@@ -37,11 +37,20 @@ func TestMimeHeaderDecodeNone(t *testing.T) {
 	}
 
 }
+
+func TestAddressPostmaster(t *testing.T) {
+	addr := &Address{User: "postmaster"}
+	str := addr.String()
+	if str != "postmaster" {
+		t.Error("it was not postmaster,", str)
+	}
+}
+
 func TestNewAddress(t *testing.T) {
 
 	addr, err := NewAddress("<hoop>")
 	if err == nil {
-		t.Error("there should be an error:", addr)
+		t.Error("there should be an error:", err)
 	}
 
 	addr, err = NewAddress(`Gogh Fir <[email protected]>`)