From fde45a5138ed813c0dae4515e2685a4d82161e46 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ferdinand=20M=C3=BCtsch?= <ferdinand@muetsch.io>
Date: Mon, 6 Mar 2023 20:31:31 +0100
Subject: [PATCH] fix: include missing mail headers (resolve #472)

---
 models/mail.go         | 33 ++++++++++++++++++++++++++++-----
 models/mail_address.go | 13 ++++++++++++-
 services/mail/smtp.go  |  2 ++
 3 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/models/mail.go b/models/mail.go
index 052002b..ca68c29 100644
--- a/models/mail.go
+++ b/models/mail.go
@@ -2,18 +2,22 @@ package models
 
 import (
 	"fmt"
+	uuid "github.com/satori/go.uuid"
 	"strings"
+	"time"
 )
 
 const HtmlType = "text/html; charset=UTF-8"
 const PlainType = "text/html; charset=UTF-8"
 
 type Mail struct {
-	From    MailAddress
-	To      MailAddresses
-	Subject string
-	Body    string
-	Type    string
+	From      MailAddress
+	To        MailAddresses
+	Subject   string
+	Body      string
+	Type      string
+	Date      time.Time
+	MessageID string
 }
 
 func (m *Mail) WithText(text string) *Mail {
@@ -28,17 +32,36 @@ func (m *Mail) WithHTML(html string) *Mail {
 	return m
 }
 
+func (m *Mail) Sanitized() *Mail {
+	if m.Type == "" {
+		m.Type = PlainType
+	}
+	if m.Date.IsZero() {
+		m.Date = time.Now()
+	}
+	if m.MessageID == "" {
+		m.MessageID = fmt.Sprintf("<%s@%s>", uuid.NewV4().String(), m.From.Domain())
+	}
+	return m
+}
+
 func (m *Mail) String() string {
 	return fmt.Sprintf("To: %s\r\n"+
 		"From: %s\r\n"+
 		"Subject: %s\r\n"+
+		"Message-ID: %s\r\n"+
+		"MIME-Version: 1.0\r\n"+
 		"Content-Type: %s\r\n"+
+		"Content-Transfer-Encoding: 8bit\r\n"+
+		"Date: %s\r\n"+
 		"\r\n"+
 		"%s\r\n",
 		strings.Join(m.To.RawStrings(), ", "),
 		m.From.String(),
 		m.Subject,
+		m.MessageID,
 		m.Type,
+		m.Date.Format(time.RFC1123Z),
 		m.Body,
 	)
 }
diff --git a/models/mail_address.go b/models/mail_address.go
index 324f63e..3ce5136 100644
--- a/models/mail_address.go
+++ b/models/mail_address.go
@@ -1,6 +1,9 @@
 package models
 
-import "regexp"
+import (
+	"regexp"
+	"strings"
+)
 
 const (
 	MailPattern      = "[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\\.[a-zA-Z0-9-.]+"
@@ -36,6 +39,14 @@ func (m MailAddress) Raw() string {
 	return ""
 }
 
+func (m MailAddress) Domain() string {
+	split := strings.Split(m.Raw(), "@")
+	if len(split) != 2 {
+		return ""
+	}
+	return split[1]
+}
+
 func (m MailAddress) Valid() bool {
 	return emailAddrRegex.Match([]byte(m))
 }
diff --git a/services/mail/smtp.go b/services/mail/smtp.go
index 4888e88..e9fc2fe 100644
--- a/services/mail/smtp.go
+++ b/services/mail/smtp.go
@@ -26,6 +26,8 @@ func NewSMTPSendingService(config conf.SMTPMailConfig) *SMTPSendingService {
 }
 
 func (s *SMTPSendingService) Send(mail *models.Mail) error {
+	mail = mail.Sanitized()
+
 	dial := smtp.Dial
 	if s.config.TLS {
 		dial = func(addr string) (*smtp.Client, error) {