diff --git a/mailpoet/lib/Cron/Workers/SendingQueue/SendingQueue.php b/mailpoet/lib/Cron/Workers/SendingQueue/SendingQueue.php
index 7fd20473f0..907586ffc9 100644
--- a/mailpoet/lib/Cron/Workers/SendingQueue/SendingQueue.php
+++ b/mailpoet/lib/Cron/Workers/SendingQueue/SendingQueue.php
@@ -427,6 +427,14 @@ class SendingQueue {
     );
   }
 
+  /**
+   * @param NewsletterEntity $newsletter
+   * @param string $textBody - The pre-processed text body of the newsletter, before any shortcodes have been processed.
+   * Leaving the shortcodes unprocessed ensures that we get the same campaignId for different subscribers, as well as
+   * for different sends of the same automatic email when link tracking is enabled.
+   *
+   * @return string
+   */
   public function calculateCampaignId(NewsletterEntity $newsletter, string $textBody): string {
     return substr(md5(implode('|', [$newsletter->getId(), $textBody, $newsletter->getSubject()])), 0, 16);
   }
diff --git a/mailpoet/tests/integration/Cron/Workers/SendingQueue/SendingQueueTest.php b/mailpoet/tests/integration/Cron/Workers/SendingQueue/SendingQueueTest.php
index da9ccabf2d..0d054aa7f4 100644
--- a/mailpoet/tests/integration/Cron/Workers/SendingQueue/SendingQueueTest.php
+++ b/mailpoet/tests/integration/Cron/Workers/SendingQueue/SendingQueueTest.php
@@ -1273,6 +1273,47 @@ class SendingQueueTest extends \MailPoetTest {
     }
   }
 
+  public function testCampaignIdDoesNotChangeIfContentStaysTheSame() {
+    $newsletter = (new \MailPoet\Test\DataFactories\Newsletter())->withSubject('Subject')->create();
+    $campaignId = $this->sendingQueueWorker->calculateCampaignId($newsletter, 'text body');
+    expect($campaignId)->equals($this->sendingQueueWorker->calculateCampaignId($newsletter, 'text body'));
+  }
+
+  public function testCampaignIdChangesIfSubjectChanges() {
+    $newsletter = (new \MailPoet\Test\DataFactories\Newsletter())->withSubject('Subject')->create();
+    $originalCampaignId = $this->sendingQueueWorker->calculateCampaignId($newsletter, 'text body');
+    $newsletter->setSubject('Subject 2');
+    $this->entityManager->persist($newsletter);
+    $this->entityManager->flush();
+    expect($originalCampaignId)->notEquals($this->sendingQueueWorker->calculateCampaignId($newsletter, 'text body'));
+  }
+
+  public function testCampaignIdRevertsIfContentReverts() {
+    $newsletter = (new \MailPoet\Test\DataFactories\Newsletter())->withSubject('Subject')->create();
+    $originalCampaignId = $this->sendingQueueWorker->calculateCampaignId($newsletter, 'text body');
+    $newsletter->setSubject('Subject 2');
+    $this->entityManager->persist($newsletter);
+    $this->entityManager->flush();
+    expect($originalCampaignId)->notEquals($this->sendingQueueWorker->calculateCampaignId($newsletter, 'text body changed'));
+    $newsletter->setSubject('Subject');
+    $this->entityManager->persist($newsletter);
+    $this->entityManager->flush();
+    expect($originalCampaignId)->equals($this->sendingQueueWorker->calculateCampaignId($newsletter, 'text body'));
+  }
+
+  public function testCampaignIdDependsOnNewsletterId() {
+    $newsletter1 = (new \MailPoet\Test\DataFactories\Newsletter())->withSubject('Subject')->create();
+    $newsletter2 = (new \MailPoet\Test\DataFactories\Newsletter())->withSubject('Subject')->create();
+    $sameContent = 'content';
+    expect($this->sendingQueueWorker->calculateCampaignId($newsletter1, $sameContent))->notEquals($this->sendingQueueWorker->calculateCampaignId($newsletter2, $sameContent));
+  }
+
+  public function testCampaignIdChangesIfContentChanges() {
+     $newsletter = (new \MailPoet\Test\DataFactories\Newsletter())->withSubject('Subject')->create();
+    $originalCampaignId = $this->sendingQueueWorker->calculateCampaignId($newsletter, 'text body');
+    expect($originalCampaignId)->notEquals($this->sendingQueueWorker->calculateCampaignId($newsletter, 'different text body'));
+  }
+
   public function _after() {
     $this->truncateEntity(SubscriberEntity::class);
     $this->truncateEntity(SubscriberSegmentEntity::class);