From e8fd12bddf032fe7863af427bcf9e59b82dffb1c Mon Sep 17 00:00:00 2001
From: Kailash Nadh <kailash@nadh.in>
Date: Sun, 19 Jan 2025 11:41:17 +0530
Subject: [PATCH] Add `List-Unsubscribe` header to opt-in confirmation mails.
 Closes #2224.

---
 cmd/init.go          |  5 +++--
 cmd/notifications.go |  4 +++-
 cmd/subscribers.go   | 14 +++++++++++++-
 3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/cmd/init.go b/cmd/init.go
index 8b5eb899..e046c8fb 100644
--- a/cmd/init.go
+++ b/cmd/init.go
@@ -76,6 +76,7 @@ type constants struct {
 		AllowExport        bool            `koanf:"allow_export"`
 		AllowWipe          bool            `koanf:"allow_wipe"`
 		RecordOptinIP      bool            `koanf:"record_optin_ip"`
+		UnsubHeader        bool            `koanf:"unsubscribe_header"`
 		Exportable         map[string]bool `koanf:"-"`
 		DomainBlocklist    []string        `koanf:"-"`
 	} `koanf:"privacy"`
@@ -483,7 +484,7 @@ func initI18n(lang string, fs stuffbin.FileSystem) *i18n.I18n {
 // initCampaignManager initializes the campaign manager.
 func initCampaignManager(q *models.Queries, cs *constants, app *App) *manager.Manager {
 	campNotifCB := func(subject string, data interface{}) error {
-		return app.sendNotification(cs.NotifyEmails, subject, notifTplCampaign, data)
+		return app.sendNotification(cs.NotifyEmails, subject, notifTplCampaign, data, nil)
 	}
 
 	if ko.Bool("passive") {
@@ -541,7 +542,7 @@ func initImporter(q *models.Queries, db *sqlx.DB, core *core.Core, app *App) *su
 				// Refresh cached subscriber counts and stats.
 				core.RefreshMatViews(true)
 
-				app.sendNotification(app.constants.NotifyEmails, subject, notifTplImport, data)
+				app.sendNotification(app.constants.NotifyEmails, subject, notifTplImport, data, nil)
 				return nil
 			},
 		}, db.DB, app.i18n)
diff --git a/cmd/notifications.go b/cmd/notifications.go
index d2415fe8..eece80ed 100644
--- a/cmd/notifications.go
+++ b/cmd/notifications.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"net/textproto"
 	"regexp"
 	"strings"
 
@@ -27,7 +28,7 @@ type notifData struct {
 }
 
 // sendNotification sends out an e-mail notification to admins.
-func (app *App) sendNotification(toEmails []string, subject, tplName string, data interface{}) error {
+func (app *App) sendNotification(toEmails []string, subject, tplName string, data interface{}, headers textproto.MIMEHeader) error {
 	if len(toEmails) == 0 {
 		return nil
 	}
@@ -48,6 +49,7 @@ func (app *App) sendNotification(toEmails []string, subject, tplName string, dat
 	m.Subject = subject
 	m.Body = body
 	m.Messenger = emailMsgr
+	m.Headers = headers
 	if err := app.manager.PushMessage(m); err != nil {
 		app.log.Printf("error sending admin notification (%s): %v", subject, err)
 		return err
diff --git a/cmd/subscribers.go b/cmd/subscribers.go
index 1f65b38e..d15dd2b7 100644
--- a/cmd/subscribers.go
+++ b/cmd/subscribers.go
@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"net/textproto"
 	"net/url"
 	"strconv"
 	"strings"
@@ -663,8 +664,19 @@ func sendOptinConfirmationHook(app *App) func(sub models.Subscriber, listIDs []i
 		out.OptinURL = fmt.Sprintf(app.constants.OptinURL, sub.UUID, qListIDs.Encode())
 		out.UnsubURL = fmt.Sprintf(app.constants.UnsubURL, dummyUUID, sub.UUID)
 
+		// Unsub headers.
+		h := textproto.MIMEHeader{}
+		h.Set(models.EmailHeaderSubscriberUUID, sub.UUID)
+
+		// Attach List-Unsubscribe headers?
+		if app.constants.Privacy.UnsubHeader {
+			unsubURL := fmt.Sprintf(app.constants.UnsubURL, dummyUUID, sub.UUID)
+			h.Set("List-Unsubscribe-Post", "List-Unsubscribe=One-Click")
+			h.Set("List-Unsubscribe", `<`+unsubURL+`>`)
+		}
+
 		// Send the e-mail.
-		if err := app.sendNotification([]string{sub.Email}, app.i18n.T("subscribers.optinSubject"), notifSubscriberOptin, out); err != nil {
+		if err := app.sendNotification([]string{sub.Email}, app.i18n.T("subscribers.optinSubject"), notifSubscriberOptin, out, h); err != nil {
 			app.log.Printf("error sending opt-in e-mail for subscriber %d (%s): %s", sub.ID, sub.UUID, err)
 			return 0, err
 		}