diff --git a/resources/sql/autopatches/20150501.calendar.1.reply.sql b/resources/sql/autopatches/20150501.calendar.1.reply.sql
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20150501.calendar.1.reply.sql
@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_calendar.calendar_event
+    ADD mailKey binary(20) NOT NULL;
diff --git a/resources/sql/autopatches/20150501.calendar.2.reply.php b/resources/sql/autopatches/20150501.calendar.2.reply.php
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20150501.calendar.2.reply.php
@@ -0,0 +1,21 @@
+<?php
+
+echo "Adding mailkeys to events.\n";
+
+$table = new PhabricatorCalendarEvent();
+$conn_w = $table->establishConnection('w');
+$iterator = new LiskMigrationIterator($table);
+foreach ($iterator as $event) {
+  $id = $event->getID();
+
+  echo "Populating event {$id}...\n";
+
+  queryfx(
+    $conn_w,
+    'UPDATE %T SET mailKey = %s WHERE id = %d',
+    $table->getTableName(),
+    Filesystem::readRandomCharacters(20),
+    $id);
+}
+
+echo "Done.\n";
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
@@ -1491,6 +1491,7 @@
     'PhabricatorCalendarEventInviteeQuery' => 'applications/calendar/query/PhabricatorCalendarEventInviteeQuery.php',
     'PhabricatorCalendarEventJoinController' => 'applications/calendar/controller/PhabricatorCalendarEventJoinController.php',
     'PhabricatorCalendarEventListController' => 'applications/calendar/controller/PhabricatorCalendarEventListController.php',
+    'PhabricatorCalendarEventMailReceiver' => 'applications/calendar/mail/PhabricatorCalendarEventMailReceiver.php',
     'PhabricatorCalendarEventPHIDType' => 'applications/calendar/phid/PhabricatorCalendarEventPHIDType.php',
     'PhabricatorCalendarEventQuery' => 'applications/calendar/query/PhabricatorCalendarEventQuery.php',
     'PhabricatorCalendarEventSearchEngine' => 'applications/calendar/query/PhabricatorCalendarEventSearchEngine.php',
@@ -1502,6 +1503,7 @@
     'PhabricatorCalendarHoliday' => 'applications/calendar/storage/PhabricatorCalendarHoliday.php',
     'PhabricatorCalendarHolidayTestCase' => 'applications/calendar/storage/__tests__/PhabricatorCalendarHolidayTestCase.php',
     'PhabricatorCalendarRemarkupRule' => 'applications/calendar/remarkup/PhabricatorCalendarRemarkupRule.php',
+    'PhabricatorCalendarReplyHandler' => 'applications/calendar/mail/PhabricatorCalendarReplyHandler.php',
     'PhabricatorCalendarSchemaSpec' => 'applications/calendar/storage/PhabricatorCalendarSchemaSpec.php',
     'PhabricatorCalendarViewController' => 'applications/calendar/controller/PhabricatorCalendarViewController.php',
     'PhabricatorCampfireProtocolAdapter' => 'infrastructure/daemon/bot/adapter/PhabricatorCampfireProtocolAdapter.php',
@@ -4830,6 +4832,7 @@
     'PhabricatorCalendarEventInviteeQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
     'PhabricatorCalendarEventJoinController' => 'PhabricatorCalendarController',
     'PhabricatorCalendarEventListController' => 'PhabricatorCalendarController',
+    'PhabricatorCalendarEventMailReceiver' => 'PhabricatorObjectMailReceiver',
     'PhabricatorCalendarEventPHIDType' => 'PhabricatorPHIDType',
     'PhabricatorCalendarEventQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
     'PhabricatorCalendarEventSearchEngine' => 'PhabricatorApplicationSearchEngine',
@@ -4841,6 +4844,7 @@
     'PhabricatorCalendarHoliday' => 'PhabricatorCalendarDAO',
     'PhabricatorCalendarHolidayTestCase' => 'PhabricatorTestCase',
     'PhabricatorCalendarRemarkupRule' => 'PhabricatorObjectRemarkupRule',
+    'PhabricatorCalendarReplyHandler' => 'PhabricatorApplicationTransactionReplyHandler',
     'PhabricatorCalendarSchemaSpec' => 'PhabricatorConfigSchemaSpec',
     'PhabricatorCalendarViewController' => 'PhabricatorCalendarController',
     'PhabricatorCampfireProtocolAdapter' => 'PhabricatorBotBaseStreamingProtocolAdapter',
diff --git a/src/applications/calendar/application/PhabricatorCalendarApplication.php b/src/applications/calendar/application/PhabricatorCalendarApplication.php
--- a/src/applications/calendar/application/PhabricatorCalendarApplication.php
+++ b/src/applications/calendar/application/PhabricatorCalendarApplication.php
@@ -74,4 +74,18 @@
     return $items;
   }
 
+  public function getMailCommandObjects() {
+    return array(
+      'event' => array(
+        'name' => pht('Email Commands: Events'),
+        'header' => pht('Interacting with Calendar Events'),
+        'object' => new PhabricatorCalendarEvent(),
+        'summary' => pht(
+          'This page documents the commands you can use to interact with '.
+          'events in Calendar. These commands work when creating new tasks '.
+          'via email and when replying to existing tasks.'),
+      ),
+    );
+  }
+
 }
diff --git a/src/applications/calendar/editor/PhabricatorCalendarEventEditor.php b/src/applications/calendar/editor/PhabricatorCalendarEventEditor.php
--- a/src/applications/calendar/editor/PhabricatorCalendarEventEditor.php
+++ b/src/applications/calendar/editor/PhabricatorCalendarEventEditor.php
@@ -209,10 +209,6 @@
     return $errors;
   }
 
-  protected function getMailTo(PhabricatorLiskDAO $object) {
-    return array($object->getUserPHID());
-  }
-
   protected function shouldPublishFeedStory(
     PhabricatorLiskDAO $object,
     array $xactions) {
@@ -222,4 +218,86 @@
   protected function supportsSearch() {
     return true;
   }
+
+  protected function shouldSendMail(
+    PhabricatorLiskDAO $object,
+    array $xactions) {
+
+    $xactions = mfilter($xactions, 'shouldHide', true);
+    return $xactions;
+  }
+
+  protected function getMailSubjectPrefix() {
+    return pht('[Calendar]');
+  }
+
+  protected function getMailTo(PhabricatorLiskDAO $object) {
+    $phids = array();
+
+    if ($object->getUserPHID()) {
+      $phids[] = $object->getUserPHID();
+    }
+    $phids[] = $this->getActingAsPHID();
+
+    $invitees = $object->getInvitees();
+    foreach ($invitees as $phid => $status) {
+      if ($status === PhabricatorCalendarEventInvitee::STATUS_ATTENDING
+        || $status === PhabricatorCalendarEventInvitee::STATUS_INVITED) {
+        $phids[] = $phid;
+      }
+    }
+
+    $phids = array_unique($phids);
+    return $phids;
+  }
+
+  public function getMailTagsMap() {
+    return array(
+      PhabricatorCalendarEventTransaction::MAILTAG_CONTENT =>
+        pht("An event's name, status, invite list, and description
+          changes."),
+      PhabricatorCalendarEventTransaction::MAILTAG_RESCHEDULE =>
+        pht("An event's start and end date and cancellation status
+          changes."),
+      PhabricatorCalendarEventTransaction::MAILTAG_OTHER =>
+        pht('Other event activity not listed above occurs.'),
+    );
+  }
+
+  protected function buildReplyHandler(PhabricatorLiskDAO $object) {
+    return id(new PhabricatorCalendarReplyHandler())
+      ->setMailReceiver($object);
+  }
+
+  protected function buildMailTemplate(PhabricatorLiskDAO $object) {
+    $id = $object->getID();
+    $name = $object->getName();
+
+    return id(new PhabricatorMetaMTAMail())
+      ->setSubject("E{$id}: {$name}")
+      ->addHeader('Thread-Topic', "E{$id}: ".$object->getName());
+  }
+
+  protected function buildMailBody(
+    PhabricatorLiskDAO $object,
+    array $xactions) {
+
+    $description = $object->getDescription();
+    $body = parent::buildMailBody($object, $xactions);
+
+    if (strlen($description)) {
+      $body->addTextSection(
+        pht('EVENT DESCRIPTION'),
+        $object->getDescription());
+    }
+
+    $body->addLinkSection(
+      pht('EVENT DETAIL'),
+      PhabricatorEnv::getProductionURI('/E'.$object->getID()));
+
+
+    return $body;
+  }
+
+
 }
diff --git a/src/applications/calendar/mail/PhabricatorCalendarEventMailReceiver.php b/src/applications/calendar/mail/PhabricatorCalendarEventMailReceiver.php
new file mode 100644
--- /dev/null
+++ b/src/applications/calendar/mail/PhabricatorCalendarEventMailReceiver.php
@@ -0,0 +1,28 @@
+<?php
+
+final class PhabricatorCalendarEventMailReceiver
+  extends PhabricatorObjectMailReceiver {
+
+  public function isEnabled() {
+    $app_class = 'PhabricatorCalendarApplication';
+    return PhabricatorApplication::isClassInstalled($app_class);
+  }
+
+  protected function getObjectPattern() {
+    return 'E[1-9]\d*';
+  }
+
+  protected function loadObject($pattern, PhabricatorUser $viewer) {
+    $id = (int)trim($pattern, 'E');
+
+    return id(new PhabricatorCalendarEventQuery())
+      ->setViewer($viewer)
+      ->withIDs(array($id))
+      ->executeOne();
+  }
+
+  protected function getTransactionReplyHandler() {
+    return new PhabricatorCalendarReplyHandler();
+  }
+
+}
diff --git a/src/applications/calendar/mail/PhabricatorCalendarReplyHandler.php b/src/applications/calendar/mail/PhabricatorCalendarReplyHandler.php
new file mode 100644
--- /dev/null
+++ b/src/applications/calendar/mail/PhabricatorCalendarReplyHandler.php
@@ -0,0 +1,15 @@
+<?php
+
+final class PhabricatorCalendarReplyHandler
+  extends PhabricatorApplicationTransactionReplyHandler {
+
+  public function validateMailReceiver($mail_receiver) {
+    if (!($mail_receiver instanceof PhabricatorCalendarEvent)) {
+      throw new Exception('Mail receiver is not a PhabricatorCalendarEvent!');
+    }
+  }
+
+  public function getObjectPrefix() {
+    return 'E';
+  }
+}
diff --git a/src/applications/calendar/storage/PhabricatorCalendarEvent.php b/src/applications/calendar/storage/PhabricatorCalendarEvent.php
--- a/src/applications/calendar/storage/PhabricatorCalendarEvent.php
+++ b/src/applications/calendar/storage/PhabricatorCalendarEvent.php
@@ -17,6 +17,7 @@
   protected $status;
   protected $description;
   protected $isCancelled;
+  protected $mailKey;
 
   protected $viewPolicy;
   protected $editPolicy;
@@ -40,6 +41,17 @@
       ->attachInvitees(array());
   }
 
+  public function save() {
+    if ($this->getDateTo() <= $this->getDateFrom()) {
+      throw new PhabricatorCalendarEventInvalidEpochException();
+    }
+
+    if (!$this->mailKey) {
+      $this->mailKey = Filesystem::readRandomCharacters(20);
+    }
+    return parent::save();
+  }
+
   private static $statusTexts = array(
     self::STATUS_AWAY => 'away',
     self::STATUS_SPORADIC => 'sporadic',
@@ -76,6 +88,7 @@
         'status' => 'uint32',
         'description' => 'text',
         'isCancelled' => 'bool',
+        'mailKey' => 'bytes20',
       ),
       self::CONFIG_KEY_SCHEMA => array(
         'userPHID_dateFrom' => array(
@@ -156,19 +169,6 @@
     return $is_attending;
   }
 
-  /**
-   * Validates data and throws exceptions for non-sensical status
-   * windows
-   */
-  public function save() {
-
-    if ($this->getDateTo() <= $this->getDateFrom()) {
-      throw new PhabricatorCalendarEventInvalidEpochException();
-    }
-
-    return parent::save();
-  }
-
 /* -(  Markup Interface  )--------------------------------------------------- */
 
 
diff --git a/src/applications/calendar/storage/PhabricatorCalendarEventTransaction.php b/src/applications/calendar/storage/PhabricatorCalendarEventTransaction.php
--- a/src/applications/calendar/storage/PhabricatorCalendarEventTransaction.php
+++ b/src/applications/calendar/storage/PhabricatorCalendarEventTransaction.php
@@ -11,6 +11,8 @@
   const TYPE_CANCEL = 'calendar.cancel';
   const TYPE_INVITE = 'calendar.invite';
 
+
+  const MAILTAG_RESCHEDULE = 'calendar-reschedule';
   const MAILTAG_CONTENT = 'calendar-content';
   const MAILTAG_OTHER = 'calendar-other';
 
@@ -442,25 +444,15 @@
     $tags = array();
     switch ($this->getTransactionType()) {
       case self::TYPE_NAME:
-        $tags[] = self::MAILTAG_CONTENT;
-        break;
-      case self::TYPE_START_DATE:
-        $tags[] = self::MAILTAG_CONTENT;
-        break;
-      case self::TYPE_END_DATE:
-        $tags[] = self::MAILTAG_CONTENT;
-        break;
       case self::TYPE_STATUS:
-        $tags[] = self::MAILTAG_OTHER;
-        break;
       case self::TYPE_DESCRIPTION:
+      case self::TYPE_INVITE:
         $tags[] = self::MAILTAG_CONTENT;
         break;
+      case self::TYPE_START_DATE:
+      case self::TYPE_END_DATE:
       case self::TYPE_CANCEL:
-        $tags[] = self::MAILTAG_CONTENT;
-        break;
-      case self::TYPE_INVITE:
-        $tags[] = self::MAILTAG_CONTENT;
+        $tags[] = self::MAILTAG_RESCHEDULE;
         break;
     }
     return $tags;