From a5a8e304e76c69c853bb5178974feeb2cfed14d4 Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Wed, 5 Apr 2023 11:34:10 +0200
Subject: [PATCH] Add ErrAuthFailed

Convenience definition for backends.

Defined in https://www.rfc-editor.org/rfc/rfc4954#section-6
---
 README.md  | 2 +-
 backend.go | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 6992498..51f4baf 100644
--- a/README.md
+++ b/README.md
@@ -107,7 +107,7 @@ type Session struct{}
 
 func (s *Session) AuthPlain(username, password string) error {
 	if username != "username" || password != "password" {
-		return errors.New("Invalid username or password")
+		return smtp.ErrAuthFailed
 	}
 	return nil
 }
diff --git a/backend.go b/backend.go
index 59cea3a..d61f3f6 100644
--- a/backend.go
+++ b/backend.go
@@ -5,6 +5,11 @@ import (
 )
 
 var (
+	ErrAuthFailed = &SMTPError{
+		Code:         535,
+		EnhancedCode: EnhancedCode{5, 7, 8},
+		Message:      "Authentication failed",
+	}
 	ErrAuthRequired = &SMTPError{
 		Code:         502,
 		EnhancedCode: EnhancedCode{5, 7, 0},