From 2a67b397c744c632af62f87a933c0a8de36ae236 Mon Sep 17 00:00:00 2001
From: Nicola Murino <nicola.murino@gmail.com>
Date: Mon, 29 May 2023 18:21:24 +0200
Subject: [PATCH] OAuth2: don't send the "*" command to cancel authentication

XOAUTH2 does not follow the SMTP AUTH RFC
---
 smtp/smtp.go | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/smtp/smtp.go b/smtp/smtp.go
index 316bcb2..a11aba4 100644
--- a/smtp/smtp.go
+++ b/smtp/smtp.go
@@ -234,8 +234,10 @@ func (c *Client) Auth(a Auth) error {
 			resp, err = a.Next(msg, code == 334)
 		}
 		if err != nil {
-			// abort the AUTH
-			_, _, _ = c.cmd(501, "*")
+			if mech != "XOAUTH2" {
+				// abort the AUTH. Not required for XOAUTH2
+				_, _, _ = c.cmd(501, "*")
+			}
 			_ = c.Quit()
 			break
 		}