From a1ce16bd5e725e8e76e6ac839537739c9eb66117 Mon Sep 17 00:00:00 2001
From: Aaron Liu <abslant.liu@gmail.com>
Date: Tue, 19 Aug 2025 09:43:23 +0800
Subject: [PATCH] fix(smtp): SMTP reset error should be ignored for
 non-standard SMTP server implementation (#2791)

---
 assets                 |  2 +-
 pkg/email/smtp.go      | 11 +++++++++++
 service/admin/tools.go |  8 ++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/assets b/assets
index f7aa0a0..2c5b89c 160000
--- a/assets
+++ b/assets
@@ -1 +1 @@
-Subproject commit f7aa0a09e22792eeeae574b585a499f0f459cede
+Subproject commit 2c5b89c59cd69a7690938f4a980468006b49b547
diff --git a/pkg/email/smtp.go b/pkg/email/smtp.go
index b9ce863..ebb5c74 100644
--- a/pkg/email/smtp.go
+++ b/pkg/email/smtp.go
@@ -2,6 +2,7 @@ package email
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"strings"
 	"time"
@@ -159,6 +160,16 @@ func (client *SMTPPool) Init() {
 
 				l := client.l.CopyWithPrefix(fmt.Sprintf("[Cid: %s]", m.cid))
 				if err := d.Send(m.msg); err != nil {
+					// Check if this is an SMTP RESET error after successful delivery
+					var sendErr *mail.SendError
+					var errParsed = errors.As(err, &sendErr)
+					if errParsed && sendErr.Reason == mail.ErrSMTPReset {
+						open = false
+						l.Debug("SMTP RESET error, closing connection...")
+						// https://github.com/wneessen/go-mail/issues/463
+						continue // Don't treat this as a delivery failure since mail was sent
+					}
+
 					l.Warning("Failed to send email: %s, Cid=%s", err, m.cid)
 				} else {
 					l.Info("Email sent to %q, title: %q.", m.to, m.subject)
diff --git a/service/admin/tools.go b/service/admin/tools.go
index e13e3a7..ac701b4 100644
--- a/service/admin/tools.go
+++ b/service/admin/tools.go
@@ -2,6 +2,7 @@ package admin
 
 import (
 	"encoding/hex"
+	"errors"
 	"net/http"
 	"strconv"
 
@@ -165,6 +166,13 @@ func (s *TestSMTPService) Test(c *gin.Context) error {
 
 	err = d.DialAndSendWithContext(c, m)
 	if err != nil {
+		// Check if this is an SMTP RESET error after successful delivery
+		var sendErr *mail.SendError
+		var errParsed = errors.As(err, &sendErr)
+		if errParsed && sendErr.Reason == mail.ErrSMTPReset {
+			return nil // Don't treat this as a delivery failure since mail was sent
+		}
+
 		return serializer.NewError(serializer.CodeInternalSetting, "Failed to send test email: "+err.Error(), err)
 	}