diff --git a/src/applications/metamta/adapter/PhabricatorMailTestAdapter.php b/src/applications/metamta/adapter/PhabricatorMailTestAdapter.php
--- a/src/applications/metamta/adapter/PhabricatorMailTestAdapter.php
+++ b/src/applications/metamta/adapter/PhabricatorMailTestAdapter.php
@@ -10,115 +10,125 @@
   const ADAPTERTYPE = 'test';
 
   private $guts = array();
-  private $config = array();
 
-  protected function validateOptions(array $options) {
-    PhutilTypeSpec::checkMap(
-      $options,
-      array());
-  }
-
-  public function newDefaultOptions() {
-    return array();
-  }
-
-  public function prepareForSend(array $config = array()) {
-    $this->config = $config;
-  }
+  private $supportsMessageID;
+  private $failPermanently;
+  private $failTemporarily;
 
-  public function setFrom($email, $name = '') {
-    $this->guts['from'] = $email;
-    $this->guts['from-name'] = $name;
+  public function setSupportsMessageID($support) {
+    $this->supportsMessageID = $support;
     return $this;
   }
 
-  public function addReplyTo($email, $name = '') {
-    if (empty($this->guts['reply-to'])) {
-      $this->guts['reply-to'] = array();
-    }
-    $this->guts['reply-to'][] = array(
-      'email' => $email,
-      'name'  => $name,
-    );
-    return $this;
-  }
-
-  public function addTos(array $emails) {
-    foreach ($emails as $email) {
-      $this->guts['tos'][] = $email;
-    }
+  public function setFailPermanently($fail) {
+    $this->failPermanently = true;
     return $this;
   }
 
-  public function addCCs(array $emails) {
-    foreach ($emails as $email) {
-      $this->guts['ccs'][] = $email;
-    }
+  public function setFailTemporarily($fail) {
+    $this->failTemporarily = true;
     return $this;
   }
 
-  public function addAttachment($data, $filename, $mimetype) {
-    $this->guts['attachments'][] = array(
-      'data' => $data,
-      'filename' => $filename,
-      'mimetype' => $mimetype,
+  public function getSupportedMessageTypes() {
+    return array(
+      PhabricatorMailEmailMessage::MESSAGETYPE,
     );
-    return $this;
   }
 
-  public function addHeader($header_name, $header_value) {
-    $this->guts['headers'][] = array($header_name, $header_value);
-    return $this;
-  }
-
-  public function setBody($body) {
-    $this->guts['body'] = $body;
-    return $this;
+  protected function validateOptions(array $options) {
+    PhutilTypeSpec::checkMap($options, array());
   }
 
-  public function setHTMLBody($html_body) {
-    $this->guts['html-body'] = $html_body;
-    return $this;
+  public function newDefaultOptions() {
+    return array();
   }
 
-  public function setSubject($subject) {
-    $this->guts['subject'] = $subject;
-    return $this;
+  public function supportsMessageIDHeader() {
+    return $this->supportsMessageID;
   }
 
-  public function supportsMessageIDHeader() {
-    return idx($this->config, 'supportsMessageIDHeader', true);
+  public function getGuts() {
+    return $this->guts;
   }
 
-  public function send() {
-    if (!empty($this->guts['fail-permanently'])) {
+  public function sendMessage(PhabricatorMailExternalMessage $message) {
+    if ($this->failPermanently) {
       throw new PhabricatorMetaMTAPermanentFailureException(
         pht('Unit Test (Permanent)'));
     }
 
-    if (!empty($this->guts['fail-temporarily'])) {
+    if ($this->failTemporarily) {
       throw new Exception(
         pht('Unit Test (Temporary)'));
     }
 
-    $this->guts['did-send'] = true;
-    return true;
-  }
+    $guts = array();
 
-  public function getGuts() {
-    return $this->guts;
-  }
+    $from = $message->getFromAddress();
+    $guts['from'] = (string)$from;
 
-  public function setFailPermanently($fail) {
-    $this->guts['fail-permanently'] = $fail;
-    return $this;
-  }
+    $reply_to = $message->getReplyToAddress();
+    if ($reply_to) {
+      $guts['reply-to'] = (string)$reply_to;
+    }
 
-  public function setFailTemporarily($fail) {
-    $this->guts['fail-temporarily'] = $fail;
-    return $this;
+    $to_addresses = $message->getToAddresses();
+    $to = array();
+    foreach ($to_addresses as $address) {
+      $to[] = (string)$address;
+    }
+    $guts['tos'] = $to;
+
+    $cc_addresses = $message->getCCAddresses();
+    $cc = array();
+    foreach ($cc_addresses as $address) {
+      $cc[] = (string)$address;
+    }
+    $guts['ccs'] = $cc;
+
+    $subject = $message->getSubject();
+    if (strlen($subject)) {
+      $guts['subject'] = $subject;
+    }
+
+    $headers = $message->getHeaders();
+    $header_list = array();
+    foreach ($headers as $header) {
+      $header_list[] = array(
+        $header->getName(),
+        $header->getValue(),
+      );
+    }
+    $guts['headers'] = $header_list;
+
+    $text_body = $message->getTextBody();
+    if (strlen($text_body)) {
+      $guts['body'] = $text_body;
+    }
+
+    $html_body = $message->getHTMLBody();
+    if (strlen($html_body)) {
+      $guts['html-body'] = $html_body;
+    }
+
+    $attachments = $message->getAttachments();
+    $file_list = array();
+    foreach ($attachments as $attachment) {
+      $file_list[] = array(
+        'data' => $attachment->getData(),
+        'filename' => $attachment->getFilename(),
+        'mimetype' => $attachment->getMimeType(),
+      );
+    }
+    $guts['attachments'] = $file_list;
+
+    $guts['did-send'] = true;
+
+    $this->guts = $guts;
   }
 
+
   public function getBody() {
     return idx($this->guts, 'body');
   }
@@ -127,4 +137,5 @@
     return idx($this->guts, 'html-body');
   }
 
+
 }
diff --git a/src/applications/metamta/receiver/__tests__/PhabricatorMailReceiverTestCase.php b/src/applications/metamta/receiver/__tests__/PhabricatorMailReceiverTestCase.php
--- a/src/applications/metamta/receiver/__tests__/PhabricatorMailReceiverTestCase.php
+++ b/src/applications/metamta/receiver/__tests__/PhabricatorMailReceiverTestCase.php
@@ -42,10 +42,10 @@
   }
 
   public function testReservedAddresses() {
-    $default_address = id(new PhabricatorMetaMTAMail())
+    $default_address = id(new PhabricatorMailEmailEngine())
       ->newDefaultEmailAddress();
 
-    $void_address = id(new PhabricatorMetaMTAMail())
+    $void_address = id(new PhabricatorMailEmailEngine())
       ->newVoidEmailAddress();
 
     $map = array(
diff --git a/src/applications/metamta/storage/__tests__/PhabricatorMetaMTAMailTestCase.php b/src/applications/metamta/storage/__tests__/PhabricatorMetaMTAMailTestCase.php
--- a/src/applications/metamta/storage/__tests__/PhabricatorMetaMTAMailTestCase.php
+++ b/src/applications/metamta/storage/__tests__/PhabricatorMetaMTAMailTestCase.php
@@ -182,21 +182,29 @@
     $supports_message_id,
     $is_first_mail) {
 
+    $user = $this->generateNewTestUser();
+    $phid = $user->getPHID();
+
     $mailer = new PhabricatorMailTestAdapter();
 
-    $mailer->prepareForSend(
-      array(
-        'supportsMessageIDHeader' => $supports_message_id,
-      ));
+    $mailer->setSupportsMessageID($supports_message_id);
 
-    $thread_id = '<somethread-12345@somedomain.tld>';
+    $thread_id = 'somethread-12345';
 
-    $mail = new PhabricatorMetaMTAMail();
-    $mail->setThreadID($thread_id, $is_first_mail);
-    $mail->sendWithMailers(array($mailer));
+    $mail = id(new PhabricatorMetaMTAMail())
+      ->setThreadID($thread_id, $is_first_mail)
+      ->addTos(array($phid))
+      ->sendWithMailers(array($mailer));
 
     $guts = $mailer->getGuts();
-    $dict = ipull($guts['headers'], 1, 0);
+
+    $headers = idx($guts, 'headers', array());
+
+    $dict = array();
+    foreach ($headers as $header) {
+      list($name, $value) = $header;
+      $dict[$name] = $value;
+    }
 
     if ($is_first_mail && $supports_message_id) {
       $expect_message_id = true;
diff --git a/src/applications/metamta/util/PhabricatorMailUtil.php b/src/applications/metamta/util/PhabricatorMailUtil.php
--- a/src/applications/metamta/util/PhabricatorMailUtil.php
+++ b/src/applications/metamta/util/PhabricatorMailUtil.php
@@ -93,13 +93,13 @@
       return true;
     }
 
-    $default_address = id(new PhabricatorMetaMTAMail())
+    $default_address = id(new PhabricatorMailEmailEngine())
       ->newDefaultEmailAddress();
     if (self::matchAddresses($address, $default_address)) {
       return true;
     }
 
-    $void_address = id(new PhabricatorMetaMTAMail())
+    $void_address = id(new PhabricatorMailEmailEngine())
       ->newVoidEmailAddress();
     if (self::matchAddresses($address, $void_address)) {
       return true;