diff --git a/Plugin/Magento/Framework/Mail/TransportInterface.php b/Plugin/Magento/Framework/Mail/TransportInterface.php
index c23e840..ca35e18 100644
--- a/Plugin/Magento/Framework/Mail/TransportInterface.php
+++ b/Plugin/Magento/Framework/Mail/TransportInterface.php
@@ -36,7 +36,6 @@ public function __construct(
      * @param \Magento\Framework\Mail\TransportInterface $subject
      * @param Closure $proceed
      * @return Closure|void $proceed
-     * @throws ReflectionException
      */
     public function aroundSendMessage(
         \Magento\Framework\Mail\TransportInterface $subject,
@@ -46,8 +45,8 @@ public function aroundSendMessage(
             return $proceed();
         }
 
-        if ($this->emailcatcher->blackListEnabled() && in_array($this->getToEmailAddress($subject), $this->getBlacklistEmailAddresses())) {
-            $subject->getMessage()->setSubject('Prevent Being Sent - Blacklisted Email Address');
+        if ($this->emailcatcher->blackListEnabled() && $this->emailInBlacklist($this->getToEmailAddress($subject))) {
+            $subject->getMessage()?->setSubject('Prevent Being Sent - Blacklisted Email Address');
             $this->saveMessage($subject);
 
             return;
@@ -88,7 +87,7 @@ private function getTemplateWhitelist(): array
     /**
      * @return array
      */
-    protected function getBlacklistEmailAddresses() : array
+    private function getBlacklistEmailAddresses() : array
     {
         return explode(',', $this->scopeConfig->getValue('emailcatcher/blacklist/block_email_addresses'));
     }
@@ -97,8 +96,33 @@ protected function getBlacklistEmailAddresses() : array
      * @param $subject
      * @return string
      */
-    protected function getToEmailAddress($subject): string
+    private function getToEmailAddress($subject): string
     {
         return $subject->getMessage()->getTo()[0]->getEmail() ?? '';
     }
+
+    /**
+     * @param string $emailAddress
+     * @return bool
+     */
+    private function domainInBlacklist(string $emailAddress): bool
+    {
+        $blacklistedDomains = explode(',', $this->scopeConfig->getValue('emailcatcher/blacklist/block_email_domains'));
+        $emailDomain = substr(strrchr($emailAddress, "@"), 1);
+
+        return in_array($emailDomain, $blacklistedDomains);
+    }
+
+    /**
+     * @param string $emailAddress
+     * @return bool
+     */
+    public function emailInBlacklist(string $emailAddress): bool
+    {
+        if ($this->domainInBlacklist($emailAddress)) {
+            return true;
+        }
+
+        return in_array($emailAddress, $this->getBlacklistEmailAddresses());
+    }
 }
diff --git a/Plugin/Magento/Framework/Mail/TransportInterfacePlugin.php b/Plugin/Magento/Framework/Mail/TransportInterfacePlugin.php
index 6c19305..accd37d 100644
--- a/Plugin/Magento/Framework/Mail/TransportInterfacePlugin.php
+++ b/Plugin/Magento/Framework/Mail/TransportInterfacePlugin.php
@@ -33,18 +33,17 @@ public function aroundSendMessage(
     {
         if (!$this->scopeConfig->isSetFlag('system/smtp/disable', ScopeInterface::SCOPE_STORE)) {
             $proceed();
-            return;
         }
 
         if ($this->emailcatcher->developmentAdminAllowedEnabled()) {
             $emailAddresses = [];
-            foreach ($subject->getMessage()->getTo() ?? [] as $to) {
+            foreach ($subject->getMessage()?->getTo() ?? [] as $to) {
                 $emailAddresses[] = $to->getEmail();
             }
-            foreach ($subject->getMessage()->getCc() ?? [] as $cc) {
+            foreach ($subject->getMessage()?->getCc() ?? [] as $cc) {
                 $emailAddresses[] = $cc->getEmail();
             }
-            foreach ($subject->getMessage()->getBcc() ?? [] as $bcc) {
+            foreach ($subject->getMessage()?->getBcc() ?? [] as $bcc) {
                 $emailAddresses[] = $bcc->getEmail();
             }
             if ($this->containsOnlyAdminUsers($emailAddresses)) {
diff --git a/etc/adminhtml/system.xml b/etc/adminhtml/system.xml
index 6d5de28..afb6eff 100644
--- a/etc/adminhtml/system.xml
+++ b/etc/adminhtml/system.xml
@@ -54,6 +54,12 @@
                         <field id="apply_blacklist">1</field>
                     </depends>
                 </field>
+                <field id="block_email_domains" type="textarea" sortOrder="10" showInWebsite="1" showInStore="1" showInDefault="1" translate="label">
+                    <label>Block Email Domains</label>
+                    <depends>
+                        <field id="apply_blacklist">1</field>
+                    </depends>
+                </field>
             </group>
             <group id="development" showInDefault="1" showInStore="1" showInWebsite="1" sortOrder="10" translate="label">
                 <label>Development</label>