Config: Can add static headers to email messages

pkg/services/notifications/email.go

@@ -22,6 +22,7 @@ type Message struct {
 	ReplyTo       []string
 	EmbeddedFiles []string
 	AttachedFiles []*AttachedFile
+	CustomHeaders map[string]string
 }
 
 func setDefaultTemplateData(cfg *setting.Cfg, data map[string]any, u *user.User) {

pkg/services/notifications/models.go

@@ -26,6 +26,7 @@ type SendEmailCommand struct {
 	ReplyTo       []string
 	EmbeddedFiles []string
 	AttachedFiles []*SendEmailAttachFile
+	CustomHeaders map[string]string
 }
 
 // SendEmailCommandSync is the command for sending emails synchronously

pkg/services/notifications/notifications.go

@@ -197,6 +197,7 @@ func (ns *NotificationService) SendEmailCommandHandlerSync(ctx context.Context,
 		AttachedFiles: cmd.AttachedFiles,
 		Subject:       cmd.Subject,
 		ReplyTo:       cmd.ReplyTo,
+		CustomHeaders: map[string]string{"slug": ns.Cfg.Slug},
 	})
 
 	if err != nil {
@@ -208,6 +209,7 @@ func (ns *NotificationService) SendEmailCommandHandlerSync(ctx context.Context,
 }
 
 func (ns *NotificationService) SendEmailCommandHandler(ctx context.Context, cmd *SendEmailCommand) error {
+	cmd.CustomHeaders = map[string]string{"slug": ns.Cfg.Slug}
 	message, err := ns.buildEmailMessage(cmd)
 
 	if err != nil {

pkg/services/notifications/smtp.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"slices"
 	"strconv"
 	"strings"
 
@@ -65,6 +66,12 @@ func (sc *SmtpClient) buildEmail(msg *Message) *gomail.Message {
 	m.SetHeader("From", msg.From)
 	m.SetHeader("To", msg.To...)
 	m.SetHeader("Subject", msg.Subject)
+	// add any allowed custom headers to the email message
+	for h, val := range msg.CustomHeaders {
+		if slices.Contains(sc.cfg.AllowedCustomHeaders, h) {
+			m.SetHeader(h, val)
+		}
+	}
 	sc.setFiles(m, msg)
 	for _, replyTo := range msg.ReplyTo {
 		m.SetAddressHeader("Reply-To", replyTo, "")

pkg/setting/setting_smtp.go

@@ -1,19 +1,24 @@
 package setting
 
-import "github.com/grafana/grafana/pkg/util"
+import (
+	"strings"
+
+	"github.com/grafana/grafana/pkg/util"
+)
 
 type SmtpSettings struct {
-	Enabled        bool
-	Host           string
-	User           string
-	Password       string
-	CertFile       string
-	KeyFile        string
-	FromAddress    string
-	FromName       string
-	EhloIdentity   string
-	StartTLSPolicy string
-	SkipVerify     bool
+	Enabled              bool
+	Host                 string
+	User                 string
+	Password             string
+	CertFile             string
+	KeyFile              string
+	FromAddress          string
+	FromName             string
+	EhloIdentity         string
+	StartTLSPolicy       string
+	SkipVerify           bool
+	AllowedCustomHeaders []string
 
 	SendWelcomeEmailOnSignUp bool
 	TemplatesPatterns        []string
@@ -34,6 +39,9 @@ func (cfg *Cfg) readSmtpSettings() {
 	cfg.Smtp.StartTLSPolicy = sec.Key("startTLS_policy").String()
 	cfg.Smtp.SkipVerify = sec.Key("skip_verify").MustBool(false)
 
+	customHeaders := sec.Key("custom_headers").MustString("")
+	cfg.Smtp.AllowedCustomHeaders = strings.Split(customHeaders, ",")
+
 	emails := cfg.Raw.Section("emails")
 	cfg.Smtp.SendWelcomeEmailOnSignUp = emails.Key("welcome_email_on_sign_up").MustBool(false)
 	cfg.Smtp.TemplatesPatterns = util.SplitString(emails.Key("templates_pattern").MustString("emails/*.html, emails/*.txt"))