优化

@@ -42,9 +42,9 @@ func (a *loginAuth) Next(fromServer []byte, more bool) ([]byte, error) {
 	}
 
 	switch {
-	case bytes.Equal(fromServer, []byte("username:")):
+	case bytes.EqualFold(fromServer, []byte("Username:")):
 		return []byte(a.username), nil
-	case bytes.Equal(fromServer, []byte("Password:")):
+	case bytes.EqualFold(fromServer, []byte("Password:")):
 		return []byte(a.password), nil
 	default:
 		return nil, fmt.Errorf("mail: unexpected server challenge: %s", fromServer)

@@ -3,7 +3,7 @@ package goemail
 import "testing"
 
 const (
-	testTo1  = "554895468@qq.com"
+	testTo1  = ""
 	testTo2  = "to2@example.com"
 	testFrom = ""
 	testpwd  = ""