diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -3411,6 +3411,7 @@
     'PhabricatorMailReceiverTestCase' => 'applications/metamta/receiver/__tests__/PhabricatorMailReceiverTestCase.php',
     'PhabricatorMailReplyHandler' => 'applications/metamta/replyhandler/PhabricatorMailReplyHandler.php',
     'PhabricatorMailRoutingRule' => 'applications/metamta/constants/PhabricatorMailRoutingRule.php',
+    'PhabricatorMailSetupCheck' => 'applications/config/check/PhabricatorMailSetupCheck.php',
     'PhabricatorMailStamp' => 'applications/metamta/stamp/PhabricatorMailStamp.php',
     'PhabricatorMailTarget' => 'applications/metamta/replyhandler/PhabricatorMailTarget.php',
     'PhabricatorMailUtil' => 'applications/metamta/util/PhabricatorMailUtil.php',
@@ -9223,6 +9224,7 @@
     'PhabricatorMailReceiverTestCase' => 'PhabricatorTestCase',
     'PhabricatorMailReplyHandler' => 'Phobject',
     'PhabricatorMailRoutingRule' => 'Phobject',
+    'PhabricatorMailSetupCheck' => 'PhabricatorSetupCheck',
     'PhabricatorMailStamp' => 'Phobject',
     'PhabricatorMailTarget' => 'Phobject',
     'PhabricatorMailUtil' => 'Phobject',
diff --git a/src/applications/config/check/PhabricatorMailSetupCheck.php b/src/applications/config/check/PhabricatorMailSetupCheck.php
new file mode 100644
--- /dev/null
+++ b/src/applications/config/check/PhabricatorMailSetupCheck.php
@@ -0,0 +1,24 @@
+<?php
+
+final class PhabricatorMailSetupCheck extends PhabricatorSetupCheck {
+
+  public function getDefaultGroup() {
+    return self::GROUP_OTHER;
+  }
+
+  protected function executeChecks() {
+    if (PhabricatorEnv::getEnvConfig('cluster.mailers')) {
+      return;
+    }
+
+    $message = pht(
+      'You haven\'t configured mailers yet, so Phabricator won\'t be able '.
+      'to send outbound mail or receive inbound mail. See the '.
+      'configuration setting cluster.mailers for details.');
+
+    $this->newIssue('cluster.mailers')
+      ->setName(pht('Mailers Not Configured'))
+      ->setMessage($message)
+      ->addPhabricatorConfig('cluster.mailers');
+  }
+}