diff --git a/src/ConfigProvider.php b/src/ConfigProvider.php
index a0c2658..97748fc 100644
--- a/src/ConfigProvider.php
+++ b/src/ConfigProvider.php
@@ -43,7 +43,7 @@
 
 class ConfigProvider
 {
-    public function __invoke()
+    public function __invoke(): array
     {
         $module = new Module();
         $config = $module->getConfig();
diff --git a/src/Service/SparkPostService.php b/src/Service/SparkPostService.php
index 61ba260..f7c9d3c 100644
--- a/src/Service/SparkPostService.php
+++ b/src/Service/SparkPostService.php
@@ -30,6 +30,13 @@ class SparkPostService extends AbstractMailService
      */
     protected $apiKey;
 
+    public const SUPPRESSION_LIST_TRANSACTIONAL = 'transactional';
+    public const SUPPRESSION_LIST_NON_TRANSACTIONAL = 'non_transactional';
+    public const SUPPRESSION_LISTS = [
+        self::SUPPRESSION_LIST_TRANSACTIONAL,
+        self::SUPPRESSION_LIST_NON_TRANSACTIONAL,
+    ];
+
     /**
      * Constructor
      */
@@ -311,6 +318,54 @@ public function registerSendingDomain(string $domain, array $options = []): bool
         return false;
     }
 
+    /**
+     * Add an email address to the suppression lists for transactional email, non-transactional email, or both
+     */
+    public function addToSuppressionList(string $emailAddress, string $reason, array $suppressionLists = self::SUPPRESSION_LISTS): void
+    {
+        $put = [
+            'recipients' => [],
+        ];
+
+        foreach($suppressionLists as $suppressionList) {
+            if(in_array($suppressionList, self::SUPPRESSION_LISTS)) {
+                $put['recipients'][] = array(
+                    'recipient' => $emailAddress,
+                    'type' => $suppressionList,
+                    'description' => $reason,
+                );
+            }
+        }
+
+        if ($put['recipients']) {
+            $response = $this->prepareHttpClient('/suppression-list/', $put)
+                ->setMethod(HttpRequest::METHOD_PUT)
+                ->send();
+
+            $this->parseResponse($response);
+        }
+    }
+
+    /**
+     * Remove an email address from the suppression lists for transactional email, non-transactional email, or both
+     */
+    public function removeFromSuppressionList(string $emailAddress, array $suppressionLists = self::SUPPRESSION_LISTS): void
+    {
+        foreach($suppressionLists as $suppressionList) {
+            if (in_array($suppressionList, self::SUPPRESSION_LISTS)) {
+                $delete = [
+                    'type' => $suppressionList,
+                ];
+
+                $response = $this->prepareHttpClient('/suppression-list/' . urlencode($emailAddress), $delete)
+                    ->setMethod(HttpRequest::METHOD_DELETE)
+                    ->send();
+
+                $this->parseResponse($response, [403, 404]);
+            }
+        }
+    }
+
     public function verifySendingDomain(string $domain, array $options = []): bool
     {
         $dkimVerify = array_key_exists('dkim_verify', $options) && $options['dkim_verify'] === true;
@@ -375,8 +430,8 @@ private function prepareHttpClient(string $uri, array $parameters = []): HttpCli
     }
 
     /**
-     * @param  HttpResponse $response
-     *
+     * @param HttpResponse $response
+     * @param int[] $successCodes
      * @throws RuntimeException
      * @return array
      */
diff --git a/tests/SlmMailTest/Service/SparkPostServiceTest.php b/tests/SlmMailTest/Service/SparkPostServiceTest.php
index df79a20..74b32cf 100644
--- a/tests/SlmMailTest/Service/SparkPostServiceTest.php
+++ b/tests/SlmMailTest/Service/SparkPostServiceTest.php
@@ -7,8 +7,6 @@
 use Laminas\Mail\Address;
 use Laminas\Mail\AddressList;
 use Laminas\Mail\Message;
-use PHPUnit\Framework\MockObject\MockBuilder;
-use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
 use ReflectionMethod;
 use SlmMail\Mail\Message\SparkPost;
@@ -43,7 +41,7 @@ private function expectApiResponse(int $statusCode = 200, string $responseBody =
         }
         $sendMessageResponse->setContent($responseBody);
 
-        $httpClientMock->expects($this->once())
+        $httpClientMock->expects($this->atLeastOnce())
             ->method('send')
             ->willReturn($sendMessageResponse);
 
@@ -190,14 +188,16 @@ public function testRemoveSendingDomain()
     {
         /** @var SparkPostService $sparkPostServiceMock */
         $sparkPostServiceMock = $this->expectApiResponse(204);
-        $this->assertNull($sparkPostServiceMock->removeSendingDomain('sparkpost-sending-domain.com'));
+        $sparkPostServiceMock->removeSendingDomain('sparkpost-sending-domain.com');
+        $this->doesNotPerformAssertions();
     }
 
     public function testRemoveNonExistingSendingDomain()
     {
         /** @var SparkPostService $sparkPostServiceMock */
         $sparkPostServiceMock = $this->expectApiResponse(404);
-        $this->assertNull($sparkPostServiceMock->removeSendingDomain('sparkpost-sending-domain.com'));
+        $sparkPostServiceMock->removeSendingDomain('sparkpost-sending-domain.com');
+        $this->doesNotPerformAssertions();
     }
 
     public function testVerifySendingDomain()
@@ -232,7 +232,7 @@ public function testVerifySendingDomainWithInvalidDkimRecord()
 
     public function testVerifyUnregisteredSendingDomain()
     {
-        //** @var SparkPostService $sparkPostServiceMock */
+        /** @var SparkPostService $sparkPostServiceMock */
         $sparkPostServiceMock = $this->expectApiResponse(
             404,
             '{"errors":[{"message":"invalid params","description":"Sending domain \'sparkpost-sending-domain.com\' is not a registered sending domain","code":"1200"}]}'
@@ -240,4 +240,44 @@ public function testVerifyUnregisteredSendingDomain()
         $this->expectException(RuntimeException::class);
         $sparkPostServiceMock->verifySendingDomain('sparkpost-sending-domain.com');
     }
+
+    public function testAddToSuppressionList()
+    {
+        /** @var SparkPostService $sparkPostServiceMock */
+        $sparkPostServiceMock = $this->expectApiResponse(200, '{"results":{"message":"Suppression List successfully updated"}}');
+        $sparkPostServiceMock->addToSuppressionList('sender@sending-domain.com', 'Permanent block after hard bounce');
+        $this->doesNotPerformAssertions();
+    }
+
+    public function testAddToTransactionalSuppressionList()
+    {
+        /** @var SparkPostService $sparkPostServiceMock */
+        $sparkPostServiceMock = $this->expectApiResponse(200, '{"results":{"message":"Suppression List successfully updated"}}');
+        $sparkPostServiceMock->addToSuppressionList('sender@sending-domain.com', 'Permanent block after hard bounce', [SparkPostService::SUPPRESSION_LIST_TRANSACTIONAL]);
+        $this->doesNotPerformAssertions();
+    }
+
+    public function testRemoveFromSuppressionList()
+    {
+        /** @var SparkPostService $sparkPostServiceMock */
+        $sparkPostServiceMock = $this->expectApiResponse(204);
+        $sparkPostServiceMock->removeFromSuppressionList('sender@sending-domain.com');
+        $this->doesNotPerformAssertions();
+    }
+
+    public function testRemoveFromTransactionalSuppressionList()
+    {
+        /** @var SparkPostService $sparkPostServiceMock */
+        $sparkPostServiceMock = $this->expectApiResponse(204);
+        $sparkPostServiceMock->removeFromSuppressionList('sender@sending-domain.com', [SparkPostService::SUPPRESSION_LIST_TRANSACTIONAL]);
+        $this->doesNotPerformAssertions();
+    }
+
+    public function testRemoveNonExistingAddressFromSuppressionList()
+    {
+        /** @var SparkPostService $sparkPostServiceMock */
+        $sparkPostServiceMock = $this->expectApiResponse(404);
+        $sparkPostServiceMock->removeFromSuppressionList('sender@sending-domain.com');
+        $this->doesNotPerformAssertions();
+    }
 }