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
@@ -487,6 +487,7 @@
     'DifferentialLintField' => 'applications/differential/customfield/DifferentialLintField.php',
     'DifferentialLintStatus' => 'applications/differential/constants/DifferentialLintStatus.php',
     'DifferentialLocalCommitsView' => 'applications/differential/view/DifferentialLocalCommitsView.php',
+    'DifferentialMailEngineExtension' => 'applications/differential/engineextension/DifferentialMailEngineExtension.php',
     'DifferentialMailView' => 'applications/differential/mail/DifferentialMailView.php',
     'DifferentialManiphestTasksField' => 'applications/differential/customfield/DifferentialManiphestTasksField.php',
     'DifferentialModernHunk' => 'applications/differential/storage/DifferentialModernHunk.php',
@@ -4400,7 +4401,6 @@
     'PhabricatorVersionedDraft' => 'applications/draft/storage/PhabricatorVersionedDraft.php',
     'PhabricatorVeryWowEnglishTranslation' => 'infrastructure/internationalization/translation/PhabricatorVeryWowEnglishTranslation.php',
     'PhabricatorViewerDatasource' => 'applications/people/typeahead/PhabricatorViewerDatasource.php',
-    'PhabricatorViewerMailStamp' => 'applications/metamta/stamp/PhabricatorViewerMailStamp.php',
     'PhabricatorWatcherHasObjectEdgeType' => 'applications/transactions/edges/PhabricatorWatcherHasObjectEdgeType.php',
     'PhabricatorWebContentSource' => 'infrastructure/contentsource/PhabricatorWebContentSource.php',
     'PhabricatorWebServerSetupCheck' => 'applications/config/check/PhabricatorWebServerSetupCheck.php',
@@ -5610,6 +5610,7 @@
     'DifferentialLintField' => 'DifferentialHarbormasterField',
     'DifferentialLintStatus' => 'Phobject',
     'DifferentialLocalCommitsView' => 'AphrontView',
+    'DifferentialMailEngineExtension' => 'PhabricatorMailEngineExtension',
     'DifferentialMailView' => 'Phobject',
     'DifferentialManiphestTasksField' => 'DifferentialCoreCustomField',
     'DifferentialModernHunk' => 'DifferentialHunk',
@@ -10148,7 +10149,6 @@
     'PhabricatorVersionedDraft' => 'PhabricatorDraftDAO',
     'PhabricatorVeryWowEnglishTranslation' => 'PhutilTranslation',
     'PhabricatorViewerDatasource' => 'PhabricatorTypeaheadDatasource',
-    'PhabricatorViewerMailStamp' => 'PhabricatorMailStamp',
     'PhabricatorWatcherHasObjectEdgeType' => 'PhabricatorEdgeType',
     'PhabricatorWebContentSource' => 'PhabricatorContentSource',
     'PhabricatorWebServerSetupCheck' => 'PhabricatorSetupCheck',
diff --git a/src/applications/differential/engineextension/DifferentialMailEngineExtension.php b/src/applications/differential/engineextension/DifferentialMailEngineExtension.php
new file mode 100644
--- /dev/null
+++ b/src/applications/differential/engineextension/DifferentialMailEngineExtension.php
@@ -0,0 +1,80 @@
+<?php
+
+final class DifferentialMailEngineExtension
+  extends PhabricatorMailEngineExtension {
+
+  const EXTENSIONKEY = 'differential';
+
+  public function supportsObject($object) {
+    return ($object instanceof DifferentialRevision);
+  }
+
+  public function newMailStampTemplates($object) {
+    return array(
+      id(new PhabricatorPHIDMailStamp())
+        ->setKey('author')
+        ->setLabel(pht('Author')),
+      id(new PhabricatorPHIDMailStamp())
+        ->setKey('reviewer')
+        ->setLabel(pht('Reviewer')),
+      id(new PhabricatorPHIDMailStamp())
+        ->setKey('blocking-reviewer')
+        ->setLabel(pht('Reviewer')),
+      id(new PhabricatorPHIDMailStamp())
+        ->setKey('resigned-reviewer')
+        ->setLabel(pht('Reviewer')),
+      id(new PhabricatorPHIDMailStamp())
+        ->setKey('revision-repository')
+        ->setLabel(pht('Revision Repository')),
+      id(new PhabricatorPHIDMailStamp())
+        ->setKey('revision-status')
+        ->setLabel(pht('Revision Status')),
+    );
+  }
+
+  public function newMailStamps($object, array $xactions) {
+    $editor = $this->getEditor();
+    $viewer = $this->getViewer();
+
+    $revision = id(new DifferentialRevisionQuery())
+      ->setViewer($viewer)
+      ->needReviewers(true)
+      ->withPHIDs(array($object->getPHID()))
+      ->executeOne();
+
+    $reviewers = array();
+    $blocking = array();
+    $resigned = array();
+    foreach ($revision->getReviewers() as $reviewer) {
+      $reviewer_phid = $reviewer->getReviewerPHID();
+
+      if ($reviewer->isResigned()) {
+        $resigned[] = $reviewer_phid;
+      } else {
+        $reviewers[] = $reviewer_phid;
+        if ($reviewer->isBlocking()) {
+          $reviewers[] = $blocking;
+        }
+      }
+    }
+
+    $this->getMailStamp('author')
+      ->setValue($revision->getAuthorPHID());
+
+    $this->getMailStamp('reviewer')
+      ->setValue($reviewers);
+
+    $this->getMailStamp('blocking-reviewer')
+      ->setValue($blocking);
+
+    $this->getMailStamp('resigned-reviewer')
+      ->setValue($resigned);
+
+    $this->getMailStamp('revision-repository')
+      ->setValue($revision->getRepositoryPHID());
+
+    $this->getMailStamp('revision-status')
+      ->setValue($revision->getModernRevisionStatus());
+  }
+
+}
diff --git a/src/applications/differential/storage/DifferentialReviewer.php b/src/applications/differential/storage/DifferentialReviewer.php
--- a/src/applications/differential/storage/DifferentialReviewer.php
+++ b/src/applications/differential/storage/DifferentialReviewer.php
@@ -69,6 +69,11 @@
     return ($this->getReviewerStatus() == $status_resigned);
   }
 
+  public function isBlocking() {
+    $status_blocking = DifferentialReviewerStatus::STATUS_BLOCKING;
+    return ($this->getReviewerStatus() == $status_blocking);
+  }
+
   public function isRejected($diff_phid) {
     $status_rejected = DifferentialReviewerStatus::STATUS_REJECTED;
 
diff --git a/src/applications/metamta/replyhandler/PhabricatorMailTarget.php b/src/applications/metamta/replyhandler/PhabricatorMailTarget.php
--- a/src/applications/metamta/replyhandler/PhabricatorMailTarget.php
+++ b/src/applications/metamta/replyhandler/PhabricatorMailTarget.php
@@ -70,14 +70,14 @@
       $body .= "\n";
       $body .= pht('STAMPS');
       $body .= "\n";
-      $body .= implode(', ', $stamps);
+      $body .= implode(' ', $stamps);
       $body .= "\n";
 
       if ($has_html) {
         $html = array();
         $html[] = phutil_tag('strong', array(), pht('STAMPS'));
         $html[] = phutil_tag('br');
-        $html[] = phutil_implode_html(', ', $stamps);
+        $html[] = phutil_implode_html(' ', $stamps);
         $html[] = phutil_tag('br');
         $html = phutil_tag('div', array(), $html);
         $html_body .= hsprintf('%s', $html);
diff --git a/src/applications/metamta/stamp/PhabricatorStringMailStamp.php b/src/applications/metamta/stamp/PhabricatorStringMailStamp.php
--- a/src/applications/metamta/stamp/PhabricatorStringMailStamp.php
+++ b/src/applications/metamta/stamp/PhabricatorStringMailStamp.php
@@ -6,11 +6,21 @@
   const STAMPTYPE = 'string';
 
   public function renderStamps($value) {
-    if (!strlen($value)) {
+    if ($value === null || $value === '') {
       return null;
     }
 
-    return $this->renderStamp($this->getKey(), $value);
+    $value = (array)$value;
+    if (!$value) {
+      return null;
+    }
+
+    $results = array();
+    foreach ($value as $v) {
+      $results[] = $this->renderStamp($this->getKey(), $v);
+    }
+
+    return $results;
   }
 
 }
diff --git a/src/applications/metamta/stamp/PhabricatorViewerMailStamp.php b/src/applications/metamta/stamp/PhabricatorViewerMailStamp.php
deleted file mode 100644
--- a/src/applications/metamta/stamp/PhabricatorViewerMailStamp.php
+++ /dev/null
@@ -1,35 +0,0 @@
-<?php
-
-final class PhabricatorViewerMailStamp
-  extends PhabricatorMailStamp {
-
-  const STAMPTYPE = 'viewer';
-
-  public function renderStamps($value) {
-    // If we're sending one mail to everyone, we never include viewer-based
-    // stamps since they'll only be accurate for one recipient. Recipients
-    // can still use the corresponding stamps with their usernames or PHIDs.
-    if (!PhabricatorMetaMTAMail::shouldMailEachRecipient()) {
-      return null;
-    }
-
-    $viewer_phid = $this->getViewer()->getPHID();
-    if (!$viewer_phid) {
-      return null;
-    }
-
-    if (!$value) {
-      return null;
-    }
-
-    $value = (array)$value;
-    $value = array_fuse($value);
-
-    if (!isset($value[$viewer_phid])) {
-      return null;
-    }
-
-    return $this->renderStamp($this->getKey());
-  }
-
-}
diff --git a/src/applications/repository/phid/PhabricatorRepositoryRepositoryPHIDType.php b/src/applications/repository/phid/PhabricatorRepositoryRepositoryPHIDType.php
--- a/src/applications/repository/phid/PhabricatorRepositoryRepositoryPHIDType.php
+++ b/src/applications/repository/phid/PhabricatorRepositoryRepositoryPHIDType.php
@@ -41,9 +41,11 @@
       $name = $repository->getName();
       $uri = $repository->getURI();
 
-      $handle->setName($monogram);
-      $handle->setFullName("{$monogram} {$name}");
-      $handle->setURI($uri);
+      $handle
+        ->setName($monogram)
+        ->setFullName("{$monogram} {$name}")
+        ->setURI($uri)
+        ->setMailStampName($monogram);
     }
   }
 
diff --git a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
--- a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
+++ b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
@@ -205,6 +205,25 @@
     return $this->mustEncrypt;
   }
 
+  public function getHeraldRuleMonograms() {
+    // Convert the stored "<123>, <456>" string into a list: "H123", "H456".
+    $list = $this->heraldHeader;
+    $list = preg_split('/[, ]+/', $list);
+
+    foreach ($list as $key => $item) {
+      $item = trim($item, '<>');
+
+      if (!is_numeric($item)) {
+        unset($list[$key]);
+        continue;
+      }
+
+      $list[$key] = 'H'.$item;
+    }
+
+    return $list;
+  }
+
   public function setIsInverseEdgeEditor($is_inverse_edge_editor) {
     $this->isInverseEdgeEditor = $is_inverse_edge_editor;
     return $this;
@@ -4109,7 +4128,7 @@
       }
     }
 
-    sort($results);
+    natcasesort($results);
 
     return $results;
   }
diff --git a/src/applications/transactions/engineextension/PhabricatorEditorMailEngineExtension.php b/src/applications/transactions/engineextension/PhabricatorEditorMailEngineExtension.php
--- a/src/applications/transactions/engineextension/PhabricatorEditorMailEngineExtension.php
+++ b/src/applications/transactions/engineextension/PhabricatorEditorMailEngineExtension.php
@@ -36,13 +36,9 @@
       ->setKey('mention')
       ->setLabel(pht('Mentioned User'));
 
-    $templates[] = id(new PhabricatorViewerMailStamp())
-      ->setKey('self-actor')
-      ->setLabel(pht('You Acted'));
-
-    $templates[] = id(new PhabricatorViewerMailStamp())
-      ->setKey('self-mention')
-      ->setLabel(pht('You Were Mentioned'));
+    $templates[] = id(new PhabricatorStringMailStamp())
+      ->setKey('herald')
+      ->setLabel(pht('Herald Rule'));
 
     return $templates;
   }
@@ -71,11 +67,8 @@
     $this->getMailStamp('mention')
       ->setValue($mentioned_phids);
 
-    $this->getMailStamp('self-actor')
-      ->setValue($editor->getActingAsPHID());
-
-    $this->getMailStamp('self-mention')
-      ->setValue($mentioned_phids);
+    $this->getMailStamp('herald')
+      ->setValue($editor->getHeraldRuleMonograms());
   }
 
 }