diff --git a/src/applications/base/controller/PhabricatorController.php b/src/applications/base/controller/PhabricatorController.php
index 33d7d84fa3..ad0055f3aa 100644
--- a/src/applications/base/controller/PhabricatorController.php
+++ b/src/applications/base/controller/PhabricatorController.php
@@ -62,9 +62,7 @@ abstract class PhabricatorController extends AphrontController {
 
     $translation = $user->getTranslation();
     if ($translation &&
-        $translation != PhabricatorEnv::getEnvConfig('translation.provider') &&
-        class_exists($translation) &&
-        is_subclass_of($translation, 'PhabricatorTranslation')) {
+        $translation != PhabricatorEnv::getEnvConfig('translation.provider')) {
       $translation = newv($translation, array());
       PhutilTranslator::getInstance()
         ->setLanguage($translation->getLanguage())
diff --git a/src/applications/differential/mail/DifferentialCommentMail.php b/src/applications/differential/mail/DifferentialCommentMail.php
index b8d32b93ab..412dcd8b63 100644
--- a/src/applications/differential/mail/DifferentialCommentMail.php
+++ b/src/applications/differential/mail/DifferentialCommentMail.php
@@ -20,6 +20,9 @@ final class DifferentialCommentMail extends DifferentialMail {
 
   protected $changedByCommit;
 
+  private $addedReviewers;
+  private $addedCCs;
+
   public function setChangedByCommit($changed_by_commit) {
     $this->changedByCommit = $changed_by_commit;
     return $this;
@@ -87,20 +90,11 @@ final class DifferentialCommentMail extends DifferentialMail {
     return $verb;
   }
 
-  protected function renderBody() {
-
-    $comment = $this->getComment();
-
-    $actor = $this->getActorName();
-    $name  = $this->getRevision()->getTitle();
-    $verb  = $this->getVerb();
-
-    $body  = array();
-
-    $body[] = "{$actor} has {$verb} the revision \"{$name}\".";
+  protected function prepareBody() {
+    parent::prepareBody();
 
     // If the commented added reviewers or CCs, list them explicitly.
-    $meta = $comment->getMetadata();
+    $meta = $this->getComment()->getMetadata();
     $m_reviewers = idx(
       $meta,
       DifferentialComment::METADATA_ADDED_REVIEWERS,
@@ -113,16 +107,32 @@ final class DifferentialCommentMail extends DifferentialMail {
     if ($load) {
       $handles = id(new PhabricatorObjectHandleData($load))->loadHandles();
       if ($m_reviewers) {
-        $body[] = 'Added Reviewers: '.$this->renderHandleList(
-          $handles,
-          $m_reviewers);
+        $this->addedReviewers = $this->renderHandleList($handles, $m_reviewers);
       }
       if ($m_cc) {
-        $body[] = 'Added CCs: '.$this->renderHandleList(
-          $handles,
-          $m_cc);
+        $this->addedCCs = $this->renderHandleList($handles, $m_cc);
       }
     }
+  }
+
+  protected function renderBody() {
+
+    $comment = $this->getComment();
+
+    $actor = $this->getActorName();
+    $name  = $this->getRevision()->getTitle();
+    $verb  = $this->getVerb();
+
+    $body  = array();
+
+    $body[] = "{$actor} has {$verb} the revision \"{$name}\".";
+
+    if ($this->addedReviewers) {
+      $body[] = 'Added Reviewers: '.$this->addedReviewers;
+    }
+    if ($this->addedCCs) {
+      $body[] = 'Added CCs: '.$this->addedCCs;
+    }
 
     $body[] = null;
 
diff --git a/src/applications/differential/mail/DifferentialMail.php b/src/applications/differential/mail/DifferentialMail.php
index 6b5a1e6d10..7cebc79069 100644
--- a/src/applications/differential/mail/DifferentialMail.php
+++ b/src/applications/differential/mail/DifferentialMail.php
@@ -78,7 +78,6 @@ abstract class DifferentialMail {
     }
 
     $cc_phids     = $this->getCCPHIDs();
-    $body         = $this->buildBody();
     $attachments  = $this->buildAttachments();
 
     $template = new PhabricatorMetaMTAMail();
@@ -90,10 +89,6 @@ abstract class DifferentialMail {
     }
 
     $template
-      ->setSubject($this->renderSubject())
-      ->setSubjectPrefix($this->getSubjectPrefix())
-      ->setVarySubjectPrefix($this->renderVaryPrefix())
-      ->setBody($body)
       ->setIsHTML($this->shouldMarkMailAsHTML())
       ->setParentMessageID($this->parentMessageID)
       ->addHeader('Thread-Topic', $this->getThreadTopic());
@@ -172,25 +167,62 @@ abstract class DifferentialMail {
     $phids = array_keys($phids);
 
     $handles = id(new PhabricatorObjectHandleData($phids))->loadHandles();
+    $objects = id(new PhabricatorObjectHandleData($phids))->loadObjects();
 
-    $event = new PhabricatorEvent(
-      PhabricatorEventType::TYPE_DIFFERENTIAL_WILLSENDMAIL,
-      array(
-        'mail' => $template,
-      )
-    );
-    PhutilEventEngine::dispatchEvent($event);
+    $to_handles = array_select_keys($handles, $to_phids);
+    $cc_handles = array_select_keys($handles, $cc_phids);
 
-    $template = $event->getValue('mail');
+    $this->prepareBody();
 
-    $mails = $reply_handler->multiplexMail(
-      $template,
-      array_select_keys($handles, $to_phids),
-      array_select_keys($handles, $cc_phids));
+    $mails = $reply_handler->multiplexMail($template, $to_handles, $cc_handles);
 
-    foreach ($mails as $mail) {
-      $mail->saveAndSend();
+    $original_translator = PhutilTranslator::getInstance();
+    if (!PhabricatorMetaMTAMail::shouldMultiplexAllMail()) {
+      $translation = PhabricatorEnv::newObjectFromConfig(
+        'translation.provider');
+      $translator = id(new PhutilTranslator())
+        ->setLanguage($translation->getLanguage())
+        ->addTranslations($translation->getTranslations());
     }
+
+    try {
+      foreach ($mails as $mail) {
+        if (PhabricatorMetaMTAMail::shouldMultiplexAllMail()) {
+          $translation = newv($mail->getTranslation($objects), array());
+          $translator = id(new PhutilTranslator())
+            ->setLanguage($translation->getLanguage())
+            ->addTranslations($translation->getTranslations());
+          PhutilTranslator::setInstance($translator);
+        }
+
+        $body =
+          $this->buildBody()."\n".
+          $reply_handler->getRecipientsSummary($to_handles, $cc_handles);
+
+        $mail
+          ->setSubject($this->renderSubject())
+          ->setSubjectPrefix($this->getSubjectPrefix())
+          ->setVarySubjectPrefix($this->renderVaryPrefix())
+          ->setBody($body);
+
+        $event = new PhabricatorEvent(
+          PhabricatorEventType::TYPE_DIFFERENTIAL_WILLSENDMAIL,
+          array(
+            'mail' => $mail,
+          )
+        );
+        PhutilEventEngine::dispatchEvent($event);
+        $mail = $event->getValue('mail');
+
+        $mail->saveAndSend();
+      }
+
+    } catch (Exception $ex) {
+      PhutilTranslator::setInstance($original_translator);
+      throw $ex;
+    }
+
+    PhutilTranslator::setInstance($original_translator);
   }
 
   protected function getMailTags() {
@@ -205,6 +237,17 @@ abstract class DifferentialMail {
     return false;
   }
 
+  /**
+   * @{method:buildBody} is called once for each e-mail recipient to allow
+   * translating text to his language. This method can be used to load data that
+   * don't need translation and use them later in @{method:buildBody}.
+   *
+   * @param
+   * @return
+   */
+  protected function prepareBody() {
+  }
+
   protected function buildBody() {
 
     $body = $this->renderBody();
@@ -369,6 +412,8 @@ EOTEXT;
     $body = array();
     foreach ($aux_fields as $field) {
       $field->setRevision($this->getRevision());
+      // TODO: Introduce and use getRequiredHandlePHIDsForMail() and load all
+      // handles in prepareBody().
       $text = $field->renderValueForMail($phase);
       if ($text !== null) {
         $body[] = $text;
diff --git a/src/applications/differential/mail/DifferentialReviewRequestMail.php b/src/applications/differential/mail/DifferentialReviewRequestMail.php
index 94cf686cbf..446579468f 100644
--- a/src/applications/differential/mail/DifferentialReviewRequestMail.php
+++ b/src/applications/differential/mail/DifferentialReviewRequestMail.php
@@ -20,6 +20,8 @@ abstract class DifferentialReviewRequestMail extends DifferentialMail {
 
   protected $comments;
 
+  private $patch;
+
   public function setComments($comments) {
     $this->comments = $comments;
     return $this;
@@ -40,6 +42,19 @@ abstract class DifferentialReviewRequestMail extends DifferentialMail {
     $this->setChangesets($changesets);
   }
 
+  protected function prepareBody() {
+    parent::prepareBody();
+
+    $inline_max_length = PhabricatorEnv::getEnvConfig(
+      'metamta.differential.inline-patches');
+    if ($inline_max_length) {
+      $patch = $this->buildPatch();
+      if (count(explode("\n", $patch)) <= $inline_max_length) {
+        $this->patch = $patch;
+      }
+    }
+  }
+
   protected function renderReviewRequestBody() {
     $revision = $this->getRevision();
 
@@ -65,14 +80,9 @@ abstract class DifferentialReviewRequestMail extends DifferentialMail {
       $body[] = null;
     }
 
-    $inline_key = 'metamta.differential.inline-patches';
-    $inline_max_length = PhabricatorEnv::getEnvConfig($inline_key);
-    if ($inline_max_length) {
-      $patch = $this->buildPatch();
-      if (count(explode("\n", $patch)) <= $inline_max_length) {
-        $body[] = 'CHANGE DETAILS';
-        $body[] = $patch;
-      }
+    if ($this->patch) {
+      $body[] = 'CHANGE DETAILS';
+      $body[] = $this->patch;
     }
 
     return implode("\n", $body);
@@ -110,14 +120,9 @@ abstract class DifferentialReviewRequestMail extends DifferentialMail {
   }
 
   private function buildPatch() {
-    $revision = $this->getRevision();
-    $revision_id = $revision->getID();
+    $diff = new DifferentialDiff();
 
-    $diffs = $revision->loadDiffs();
-    $diff_number = count($diffs);
-    $diff = array_pop($diffs);
-
-    $diff->attachChangesets($diff->loadChangesets());
+    $diff->attachChangesets($this->getChangesets());
     // TODO: We could batch this to improve performance.
     foreach ($diff->getChangesets() as $changeset) {
       $changeset->attachHunks($changeset->loadHunks());
diff --git a/src/applications/metamta/replyhandler/PhabricatorMailReplyHandler.php b/src/applications/metamta/replyhandler/PhabricatorMailReplyHandler.php
index 689b37afd8..00bfea095e 100644
--- a/src/applications/metamta/replyhandler/PhabricatorMailReplyHandler.php
+++ b/src/applications/metamta/replyhandler/PhabricatorMailReplyHandler.php
@@ -71,6 +71,22 @@ abstract class PhabricatorMailReplyHandler {
     return null;
   }
 
+  final public function getRecipientsSummary(
+    array $to_handles,
+    array $cc_handles) {
+    assert_instances_of($to_handles, 'PhabricatorObjectHandle');
+    assert_instances_of($cc_handles, 'PhabricatorObjectHandle');
+
+    $body = '';
+    if ($to_handles) {
+      $body .= "To: ".implode(', ', mpull($to_handles, 'getName'))."\n";
+    }
+    if ($cc_handles) {
+      $body .= "Cc: ".implode(', ', mpull($cc_handles, 'getName'))."\n";
+    }
+    return $body;
+  }
+
   final public function multiplexMail(
     PhabricatorMetaMTAMail $mail_template,
     array $to_handles,
@@ -115,13 +131,12 @@ abstract class PhabricatorMailReplyHandler {
     $body = $mail_template->getBody();
     $body .= "\n";
     if ($to_handles) {
-      $body .= "To: ".implode(', ', mpull($to_handles, 'getName'))."\n";
       $add_headers['X-Phabricator-To'] = $this->formatPHIDList($to_handles);
     }
     if ($cc_handles) {
-      $body .= "Cc: ".implode(', ', mpull($cc_handles, 'getName'))."\n";
       $add_headers['X-Phabricator-Cc'] = $this->formatPHIDList($cc_handles);
     }
+    $body .= $this->getRecipientsSummary($to_handles, $cc_handles);
 
     foreach ($recipients as $recipient) {
       $mail = clone $mail_template;
diff --git a/src/applications/metamta/storage/PhabricatorMetaMTAMail.php b/src/applications/metamta/storage/PhabricatorMetaMTAMail.php
index f6ccdbe25d..e189296885 100644
--- a/src/applications/metamta/storage/PhabricatorMetaMTAMail.php
+++ b/src/applications/metamta/storage/PhabricatorMetaMTAMail.php
@@ -119,6 +119,28 @@ final class PhabricatorMetaMTAMail extends PhabricatorMetaMTADAO {
     return $this;
   }
 
+  public function getTranslation(array $objects) {
+    $default_translation = PhabricatorEnv::getEnvConfig('translation.provider');
+    $return = null;
+    $recipients = array_merge(
+      idx($this->parameters, 'to', array()),
+      idx($this->parameters, 'cc', array()));
+    foreach (array_select_keys($objects, $recipients) as $object) {
+      $translation = null;
+      if ($object instanceof PhabricatorUser) {
+        $translation = $object->getTranslation();
+      }
+      if (!$translation) {
+        $translation = $default_translation;
+      }
+      if ($return && $translation != $return) {
+        return $default_translation;
+      }
+      $return = $translation;
+    }
+    return $return;
+  }
+
   public function addHeader($name, $value) {
     $this->parameters['headers'][$name] = $value;
     return $this;
diff --git a/src/applications/people/storage/PhabricatorUser.php b/src/applications/people/storage/PhabricatorUser.php
index 56482894a6..8786196b89 100644
--- a/src/applications/people/storage/PhabricatorUser.php
+++ b/src/applications/people/storage/PhabricatorUser.php
@@ -96,6 +96,19 @@ final class PhabricatorUser extends PhabricatorUserDAO implements PhutilPerson {
     return $this->sex;
   }
 
+  public function getTranslation() {
+    try {
+      if ($this->translation &&
+          class_exists($this->translation) &&
+          is_subclass_of($this->translation, 'PhabricatorTranslation')) {
+        return $this->translation;
+      }
+    } catch (PhutilMissingSymbolException $ex) {
+      return null;
+    }
+    return null;
+  }
+
   public function isLoggedIn() {
     return !($this->getPHID() === null);
   }