From 846e3b9a372c124c553aeb6858e8d650dffaa95a Mon Sep 17 00:00:00 2001
From: Nicolai Langfeldt <nicolai.langfeldt@schibsted.no>
Date: Thu, 24 Apr 2025 11:17:35 +0200
Subject: [PATCH] Support HELO

---
 client.go | 13 +++++++++++++
 server.go |  1 +
 2 files changed, 14 insertions(+)

diff --git a/client.go b/client.go
index 5579a1c..3605e6d 100644
--- a/client.go
+++ b/client.go
@@ -92,12 +92,25 @@ func sendMail(e *mail.Envelope, config *relayConfig) error {
 }
 
 func handshake(client *smtp.Client, config *relayConfig, tlsConfig *tls.Config) error {
+	if config.HeloHost != "" {
+		if err := client.Hello(config.HeloHost); err != nil {
+			return errors.Wrap(err, "HELO error")
+		}
+	}
+
 	if config.STARTTLS {
 		if err := client.StartTLS(tlsConfig); err != nil {
 			return errors.Wrap(err, "starttls error")
 		}
+		// Re-HELO after STARTTLS
+		if config.HeloHost != "" {
+			if err := client.Hello(config.HeloHost); err != nil {
+				return errors.Wrap(err, "HELO error")
+			}
+		}
 	}
 
+
 	var auth smtp.Auth
 	if config.LoginAuthType {
 		auth = LoginAuth(config.Username, config.Password)
diff --git a/server.go b/server.go
index cd9994f..96bc218 100644
--- a/server.go
+++ b/server.go
@@ -64,6 +64,7 @@ type relayConfig struct {
 	Username      string `json:"smtp_username"`
 	Password      string `json:"smtp_password"`
 	SkipVerify    bool   `json:"smtp_skip_cert_verify"`
+	HeloHost      string `json:"smtp_helo"`
 }
 
 // mailRelayProcessor decorator relays emails to another SMTP server.