diff --git a/src/config.php b/src/config.php
index 120e66f3..9aff1f49 100644
--- a/src/config.php
+++ b/src/config.php
@@ -28,20 +28,23 @@
         // An API key to use for triggering tasks and notifications (min. 16 characters)
         //'apiKey' => 'aBcDeFgHiJkLmNoP',
 
-        //Whether to validate incoming webhook requests using a verification key
-        //validateWebhookRequests => true,
+        // Whether one-click unsubscribe headers should be added to emails.
+        //'addOneClickUnsubscribeHeaders' => true,
+
+        // Whether to validate incoming webhook requests using a verification key
+        //'validateWebhookRequests' => true,
 
         // A webhook signing secret provided by MailerSend to validate incoming webhook requests
-        //mailersendWebhookSigningSecret => 'aBcDeFgHiJkLmNoP123',
+        //'mailersendWebhookSigningSecret' => 'aBcDeFgHiJkLmNoP123',
 
         // A webhook signing key provided by Mailgun to validate incoming webhook requests
-        //mailgunWebhookSigningKey => 'key-aBcDeFgHiJkLmNoP',
+        //'mailgunWebhookSigningKey' => 'key-aBcDeFgHiJkLmNoP',
 
         // A webhook verification key provided by SendGrid to validate incoming webhook requests
-        //sendgridWebhookVerificationKey => 'aBcDeFgHiJkLmNoP123==',
+        //'sendgridWebhookVerificationKey' => 'aBcDeFgHiJkLmNoP123==',
 
         // The allowed IP addresses for incoming webhook requests from Postmark
-        //postmarkAllowedIpAddresses => [
+        //'postmarkAllowedIpAddresses' => [
         //    '3.134.147.250',
         //    '50.31.156.6',
         //    '50.31.156.77',
diff --git a/src/controllers/TrackerController.php b/src/controllers/TrackerController.php
index d12a6009..5166cddb 100644
--- a/src/controllers/TrackerController.php
+++ b/src/controllers/TrackerController.php
@@ -16,6 +16,16 @@
 
 class TrackerController extends BaseMessageController
 {
+    /**
+     * @inheritdoc
+     */
+    public $enableCsrfValidation = false;
+
+    /**
+     * @var bool Disable Snaptcha validation
+     */
+    public bool $enableSnaptchaValidation = false;
+
     /**
      * @inheritdoc
      */
@@ -120,6 +130,32 @@ public function actionUnsubscribe(): ?Response
         ]);
     }
 
+    /**
+     * Tracks a one-click unsubscribe.
+     * https://postmarkapp.com/support/article/1299-how-to-include-a-list-unsubscribe-header
+     *
+     * @since 2.15.0
+     */
+    public function actionOneClickUnsubscribe(): ?Response
+    {
+        // Ignore if a non-POST requests but don’t require it, since anti-spam tools may send GET requests.
+        if (!$this->request->getIsPost()) {
+            return $this->asRaw('');
+        }
+
+        // Get contact and sendout
+        $contact = $this->getContact();
+        $sendout = $this->getSendout();
+
+        if ($contact === null || $sendout === null) {
+            throw new NotFoundHttpException(Craft::t('campaign', 'Unsubscribe link is invalid.'));
+        }
+
+        Campaign::$plugin->tracker->unsubscribe($contact, $sendout);
+
+        return $this->asRaw('OK');
+    }
+
     /**
      * Gets a contact by CID in param.
      */
diff --git a/src/elements/ContactElement.php b/src/elements/ContactElement.php
index bd33b2c4..27a3267b 100755
--- a/src/elements/ContactElement.php
+++ b/src/elements/ContactElement.php
@@ -785,7 +785,7 @@ public function getMailingListSubscriptionStatus(int $mailingListId): string
     {
         /** @var ContactMailingListRecord|null $contactMailingList */
         $contactMailingList = ContactMailingListRecord::find()
-            ->select('subscriptionStatus')
+            ->select(['subscriptionStatus'])
             ->where([
                 'contactId' => $this->id,
                 'mailingListId' => $mailingListId,
@@ -1075,7 +1075,7 @@ private function getMailingListsWithStatus(string $subscriptionStatus = null): a
 
         /** @var ContactMailingListRecord[] $contactMailingLists */
         $contactMailingLists = ContactMailingListRecord::find()
-            ->select('mailingListId')
+            ->select(['mailingListId'])
             ->where($condition)
             ->all();
 
diff --git a/src/elements/MailingListElement.php b/src/elements/MailingListElement.php
index 39eee212..78676a28 100755
--- a/src/elements/MailingListElement.php
+++ b/src/elements/MailingListElement.php
@@ -656,7 +656,7 @@ private function getContactCount(string $subscriptionStatus = null): int
     private function getContactsBySubscriptionStatus(string $subscriptionStatus = null): array
     {
         $query = ContactMailingListRecord::find()
-            ->select('contactId')
+            ->select(['contactId'])
             ->where(['mailingListId' => $this->id]);
 
         if ($subscriptionStatus) {
diff --git a/src/elements/SendoutElement.php b/src/elements/SendoutElement.php
index 9a28a0e3..7feeda29 100755
--- a/src/elements/SendoutElement.php
+++ b/src/elements/SendoutElement.php
@@ -840,7 +840,7 @@ public function getNotificationEmailAddresses(): array
         }
 
         return ContactElement::find()
-            ->select('email')
+            ->select(['email'])
             ->id($this->notificationContactIds)
             ->column();
     }
diff --git a/src/elements/db/CampaignElementQuery.php b/src/elements/db/CampaignElementQuery.php
index f84673fb..b0e1ff7a 100755
--- a/src/elements/db/CampaignElementQuery.php
+++ b/src/elements/db/CampaignElementQuery.php
@@ -95,12 +95,12 @@ protected function beforePrepare(): bool
 
         // Add the last sent date
         $sendoutQuery = SendoutRecord::find()
-            ->select('campaignId, MAX([[lastSent]]) AS lastSent')
-            ->groupBy('campaignId');
+            ->select(['campaignId', 'lastSent' => 'MAX([[lastSent]])'])
+            ->groupBy(['campaignId']);
 
-        $this->query->addSelect('lastSent');
+        $this->query->addSelect(['lastSent']);
         $this->subQuery->leftJoin(['campaign_sendouts' => $sendoutQuery], '[[campaign_sendouts.campaignId]] = [[campaign_campaigns.id]]');
-        $this->subQuery->select('campaign_sendouts.lastSent AS lastSent');
+        $this->subQuery->select(['lastSent' => 'campaign_sendouts.lastSent']);
 
         // Filter by campaign types in sites that have not been deleted
         $this->subQuery->innerJoin(CampaignTypeRecord::tableName() . ' campaign_campaigntypes', '[[campaign_campaigntypes.id]] = [[campaign_campaigns.campaignTypeId]]');
diff --git a/src/elements/db/ContactElementQuery.php b/src/elements/db/ContactElementQuery.php
index 44a28220..cea126c1 100644
--- a/src/elements/db/ContactElementQuery.php
+++ b/src/elements/db/ContactElementQuery.php
@@ -145,9 +145,9 @@ protected function beforePrepare(): bool
         }
 
         if ($this->mailingListId) {
-            $this->query->addSelect('subscriptionStatus');
+            $this->query->addSelect(['subscriptionStatus']);
             $this->subQuery->innerJoin(ContactMailingListRecord::tableName() . ' campaign_contacts_mailinglists', '[[campaign_contacts.id]] = [[campaign_contacts_mailinglists.contactId]]');
-            $this->subQuery->select('campaign_contacts_mailinglists.subscriptionStatus AS subscriptionStatus');
+            $this->subQuery->select(['subscriptionStatus' => 'campaign_contacts_mailinglists.subscriptionStatus']);
             $this->subQuery->andWhere(Db::parseParam('campaign_contacts_mailinglists.mailingListId', $this->mailingListId));
         } else {
             // Add a dummy subscriptionStatus value to prevent sorted queries from failing
diff --git a/src/elements/db/MailingListElementQuery.php b/src/elements/db/MailingListElementQuery.php
index 8ab1dc33..8fc4910d 100755
--- a/src/elements/db/MailingListElementQuery.php
+++ b/src/elements/db/MailingListElementQuery.php
@@ -117,7 +117,7 @@ protected function beforePrepare(): bool
         }
 
         $this->subQuery->innerJoin(MailingListTypeRecord::tableName() . ' campaign_mailinglisttypes', '[[campaign_mailinglisttypes.id]] = [[campaign_mailinglists.mailingListTypeId]]');
-        $this->subQuery->select('campaign_mailinglisttypes.name AS mailingListType');
+        $this->subQuery->select(['mailingListType' => 'campaign_mailinglisttypes.name']);
 
         $this->subQuery->innerJoin(Table::SITES . ' sites', '[[sites.id]] = [[campaign_mailinglisttypes.siteId]]');
         $this->subQuery->andWhere(['[[sites.dateDeleted]]' => null]);
diff --git a/src/models/SettingsModel.php b/src/models/SettingsModel.php
index 4d02ad4d..d6285999 100644
--- a/src/models/SettingsModel.php
+++ b/src/models/SettingsModel.php
@@ -42,6 +42,12 @@ class SettingsModel extends Model
      */
     public string $apiKey;
 
+    /**
+     * @var bool Whether one-click unsubscribe headers should be added to emails.
+     * @since 2.15.0
+     */
+    public bool $addOneClickUnsubscribeHeaders = true;
+
     /**
      * @var bool Whether to validate incoming webhook requests using a signing key or secret
      * @since 2.10.0
diff --git a/src/services/SendoutsService.php b/src/services/SendoutsService.php
index 5492e5ed..f0bcb389 100755
--- a/src/services/SendoutsService.php
+++ b/src/services/SendoutsService.php
@@ -13,6 +13,7 @@
 use craft\helpers\Queue;
 use craft\helpers\StringHelper;
 use craft\helpers\UrlHelper;
+use craft\mail\Message;
 use DateTime;
 use DOMDocument;
 use DOMElement;
@@ -87,7 +88,7 @@ public function getSendoutBySid(string $sid): ?SendoutElement
         }
 
         $sendoutId = SendoutRecord::find()
-            ->select('id')
+            ->select(['id'])
             ->where(['sid' => $sid])
             ->scalar();
 
@@ -299,9 +300,18 @@ public function sendEmail(SendoutElement $sendout, ContactElement $contact, int
             Campaign::$plugin->mailer->useFileTransport = true;
         }
 
-        // Create message
-        $message = Campaign::$plugin->mailer->compose()
-            ->setFrom([$sendout->fromEmail => $sendout->fromName])
+        /** @var Message $message */
+        $message = Campaign::$plugin->mailer->compose();
+
+        if (Campaign::$plugin->settings->addOneClickUnsubscribeHeaders) {
+            // Use the one-click unsubscribe controller action.
+            $oneClickUnsubscribeUrl = str_replace('campaign/t/unsubscribe', 'campaign/t/one-click-unsubscribe', $contact->getUnsubscribeUrl($sendout));
+
+            $message->setHeader('List-Unsubscribe-Post', 'List-Unsubscribe=One-Click')
+                ->setHeader('List-Unsubscribe', $oneClickUnsubscribeUrl);
+        }
+
+        $message->setFrom([$sendout->fromEmail => $sendout->fromName])
             ->setTo($contact->email)
             ->setSubject($sendout->subject)
             ->setHtmlBody($htmlBody)
@@ -543,7 +553,7 @@ private function getMailingListById(int $mailingListId): MailingListElement
     private function getExcludedMailingListRecipientsQuery(SendoutElement $sendout): ActiveQuery
     {
         return ContactMailingListRecord::find()
-            ->select('contactId')
+            ->select(['contactId'])
             ->where([
                 'mailingListId' => $sendout->excludedMailingListIds,
                 'subscriptionStatus' => 'subscribed',
@@ -556,7 +566,7 @@ private function getExcludedMailingListRecipientsQuery(SendoutElement $sendout):
     private function getSentRecipientsQuery(SendoutElement $sendout, bool $todayOnly = false): ActiveQuery
     {
         $query = ContactCampaignRecord::find()
-            ->select('contactId')
+            ->select(['contactId'])
             ->where(['sendoutId' => $sendout->id])
             ->andWhere(['not', ['sent' => null]]);
 
@@ -594,7 +604,7 @@ private function getPendingRecipientsStandardIds(SendoutElement $sendout): array
 
         // Get contacts subscribed to sendout’s mailing lists
         $query = ContactMailingListRecord::find()
-            ->select('contactId')
+            ->select(['contactId'])
             ->andWhere($baseCondition);
 
         // Ensure contacts have not complained, bounced, or been blocked (in contact record)
@@ -648,8 +658,8 @@ private function getPendingRecipientsStandard(SendoutElement $sendout, int $limi
 
         /** @var array $recipients */
         $recipients = ContactMailingListRecord::find()
-            ->select(['contactId', 'min([[mailingListId]]) as mailingListId', 'min([[subscribed]]) as subscribed'])
-            ->groupBy('contactId')
+            ->select(['contactId', 'mailingListId' => 'MIN([[mailingListId]])', 'subscribed' => 'MIN([[subscribed]])'])
+            ->groupBy(['contactId'])
             ->where($baseCondition)
             ->andWhere(['contactId' => $contactIds])
             ->orderBy(['contactId' => SORT_ASC])
diff --git a/tests/pest/Helpers.php b/tests/pest/Helpers.php
index 336139a9..27ba05bf 100644
--- a/tests/pest/Helpers.php
+++ b/tests/pest/Helpers.php
@@ -138,13 +138,13 @@ function cleanup(): void
 {
     $campaignType = Campaign::$plugin->campaignTypes->getCampaignTypeByHandle(App::env('TEST_CAMPAIGN_TYPE_HANDLE'));
     $campaignIds = CampaignRecord::find()
-        ->select('id')
+        ->select(['id'])
         ->where(['campaignTypeId' => $campaignType->id])
         ->column();
 
     $mailingListType = Campaign::$plugin->mailingListTypes->getMailingListTypeByHandle(App::env('TEST_MAILING_LIST_TYPE_HANDLE'));
     $mailingListIds = MailingListRecord::find()
-        ->select('id')
+        ->select(['id'])
         ->where(['mailingListTypeId' => $mailingListType->id])
         ->column();
 
@@ -153,7 +153,7 @@ function cleanup(): void
 
     $userGroup = Craft::$app->userGroups->getGroupByHandle(App::env('TEST_USER_GROUP_HANDLE'));
     $userIds = User::find()
-        ->select('id')
+        ->select(['id'])
         ->groupId($userGroup->id)
         ->column();