diff --git a/conf/default.conf.php b/conf/default.conf.php
index a99149a64e..ea0200e77f 100644
--- a/conf/default.conf.php
+++ b/conf/default.conf.php
@@ -1,362 +1,369 @@
 <?php
 
 /*
  * Copyright 2011 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *   http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 
 return array(
 
   // The root URI which Phabricator is installed on.
   // Example: "http://phabricator.example.com/"
   'phabricator.base-uri'        => null,
 
   // If you have multiple environments, provide the production environment URI
   // here so that emails, etc., generated in development/sandbox environments
   // contain the right links.
   'phabricator.production-uri'  => null,
 
   // Setting this to 'true' will invoke a special setup mode which helps guide
   // you through setting up Phabricator.
   'phabricator.setup'           => false,
 
   // The default PHID for users who haven't uploaded a profile image. It should
   // be 50x50px.
   'user.default-profile-image-phid' => 'PHID-FILE-4d61229816cfe6f2b2a3',
 
 // -- DarkConsole ----------------------------------------------------------- //
 
   // DarkConsole is a administrative debugging/profiling tool built into
   // Phabricator. You can leave it disabled unless you're developing against
   // Phabricator.
 
   // Determines whether or not DarkConsole is available. DarkConsole exposes
   // some data like queries and stack traces, so you should be careful about
   // turning it on in production (although users can not normally see it, even
   // if the deployment configuration enables it).
   'darkconsole.enabled'         => false,
 
   // Always enable DarkConsole, even for logged out users. This potentially
   // exposes sensitive information to users, so make sure untrusted users can
   // not access an install running in this mode. You should definitely leave
   // this off in production. It is only really useful for using DarkConsole
   // utilties to debug or profile logged-out pages. You must set
   // 'darkconsole.enabled' to use this option.
   'darkconsole.always-on'       => false,
 
 
   // Allows you to mask certain configuration values from appearing in the
   // "Config" tab of DarkConsole.
   'darkconsole.config-mask'     => array(
     'mysql.pass',
     'amazon-ses.secret-key',
     'recaptcha.private-key',
     'phabricator.csrf-key',
     'facebook.application-secret',
     'github.application-secret',
   ),
 
 // --  MySQL  --------------------------------------------------------------- //
 
   // The username to use when connecting to MySQL.
   'mysql.user' => 'root',
 
   // The password to use when connecting to MySQL.
   'mysql.pass' => '',
 
   // The MySQL server to connect to.
   'mysql.host' => 'localhost',
 
 // -- Email ----------------------------------------------------------------- //
 
   // Some Phabricator tools send email notifications, e.g. when Differential
   // revisions are updated or Maniphest tasks are changed. These options allow
   // you to configure how email is delivered.
 
   // You can test your mail setup by going to "MetaMTA" in the web interface,
   // clicking "Send New Message", and then composing a message.
 
   // Default address to send mail "From".
   'metamta.default-address'     => 'noreply@example.com',
 
   // Domain used to generate Message-IDs.
   'metamta.domain'              => 'example.com',
 
   // When a user takes an action which generates an email notification (like
   // commenting on a Differential revision), Phabricator can either send that
   // mail "From" the user's email address (like "alincoln@logcabin.com") or
   // "From" the 'metamta.default-address' address. The user experience is
   // generally better if Phabricator uses the user's real address as the "From"
   // since the messages are easier to organize when they appear in mail clients,
   // but this will only work if the server is authorized to send email on behalf
   // of the "From" domain. Practically, this means:
   //    - If you are doing an install for Example Corp and all the users will
   //      have corporate @corp.example.com addresses and any hosts Phabricator
   //      is running on are authorized to send email from corp.example.com,
   //      you can enable this to make the user experience a little better.
   //    - If you are doing an install for an open source project and your
   //      users will be registering via Facebook and using personal email
   //      addresses, you MUST NOT enable this or virtually all of your outgoing
   //      email will vanish into SFP blackholes.
   //    - If your install is anything else, you're much safer leaving this
   //      off since the risk in turning it on is that your outgoing mail will
   //      mostly never arrive.
   'metamta.can-send-as-user'    => false,
 
   // Adapter class to use to transmit mail to the MTA. The default uses
   // PHPMailerLite, which will invoke "sendmail". This is appropriate
   // if sendmail actually works on your host, but if you haven't configured mail
   // it may not be so great. You can also use Amazon SES, by changing this to
   // 'PhabricatorMailImplementationAmazonSESAdapter', signing up for SES, and
   // filling in your 'amazon-ses.access-key' and 'amazon-ses.secret-key' below.
   'metamta.mail-adapter'        =>
     'PhabricatorMailImplementationPHPMailerLiteAdapter',
 
   // When email is sent, try to hand it off to the MTA immediately. This may
   // be worth disabling if your MTA infrastructure is slow or unreliable. If you
   // disable this option, you must run the 'metamta_mta.php' daemon or mail
   // won't be handed off to the MTA. If you're using Amazon SES it can be a
   // little slugish sometimes so it may be worth disabling this and moving to
   // the daemon after you've got your install up and running. If you have a
   // properly configured local MTA it should not be necessary to disable this.
   'metamta.send-immediately'    => true,
 
   // If you're using Amazon SES to send email, provide your AWS access key
   // and AWS secret key here. To set up Amazon SES with Phabricator, you need
   // to:
   //  - Make sure 'metamta.mail-adapter' is set to:
   //    "PhabricatorMailImplementationAmazonSESAdapter"
   //  - Make sure 'metamta.can-send-as-user' is false.
   //  - Make sure 'metamta.default-address' is configured to something sensible.
   //  - Make sure 'metamta.default-address' is a validated SES "From" address.
   'amazon-ses.access-key'       =>  null,
   'amazon-ses.secret-key'       =>  null,
 
   // You can configure a reply handler domain so that email sent from Maniphest
   // will have a special "Reply To" address like "T123+82+af19f@example.com"
   // that allows recipients to reply by email and interact with tasks. For
   // instructions on configurating reply handlers, see the article
   // "Configuring Inbound Email" in the Phabricator documentation. By default,
   // this is set to 'null' and Phabricator will use a generic 'noreply@' address
   // or the address of the acting user instead of a special reply handler
   // address (see 'metamta.default-address'). If you set a domain here,
   // Phabricator will begin generating private reply handler addresses. See
   // also 'metamta.maniphest.reply-handler' to further configure behavior.
   // This key should be set to the domain part after the @, like "example.com".
   'metamta.maniphest.reply-handler-domain' => null,
 
   // You can follow the instructions in "Configuring Inbound Email" in the
   // Phabricator documentation and set 'metamta.maniphest.reply-handler-domain'
   // to support updating Maniphest tasks by email. If you want more advanced
   // customization than this provides, you can override the reply handler
   // class with an implementation of your own. This will allow you to do things
   // like have a single public reply handler or change how private reply
   // handlers are generated and validated.
   // This key should be set to a loadable subclass of
   // PhabricatorMailReplyHandler (and possibly of ManiphestReplyHandler).
   'metamta.maniphest.reply-handler' => 'ManiphestReplyHandler',
 
+  // Prefix prepended to mail sent by Maniphest. You can change this to
+  // distinguish between testing and development installs, for example.
+  'metamta.maniphest.subject-prefix' => '[Maniphest]',
+
   // See 'metamta.maniphest.reply-handler-domain'. This does the same thing,
   // but allows email replies via Differential.
   'metamta.differential.reply-handler-domain' => null,
 
   // See 'metamta.maniphest.reply-handler'. This does the same thing, but
   // affects Differential.
   'metamta.differential.reply-handler' => 'DifferentialReplyHandler',
 
+  // Prefix prepended to mail sent by Differential.
+  'metamta.differential.subject-prefix' => '[Differential]',
+
 
 // -- Auth ------------------------------------------------------------------ //
 
   // Can users login with a username/password, or by following the link from
   // a password reset email? You can disable this and configure one or more
   // OAuth providers instead.
   'auth.password-auth-enabled'  => true,
 
   // Maximum number of simultaneous web sessions each user is permitted to have.
   // Setting this to "1" will prevent a user from logging in on more than one
   // browser at the same time.
   'auth.sessions.web'           => 5,
 
   // Maximum number of simultaneous Conduit sessions each user is permitted
   // to have.
   'auth.sessions.conduit'       => 3,
 
 
 // -- Accounts -------------------------------------------------------------- //
 
   // Is basic account information (email, real name, profile picture) editable?
   // If you set up Phabricator to automatically synchronize account information
   // from some other authoritative system, you can disable this to ensure
   // information remains consistent across both systems.
   'account.editable'            => true,
 
 
 // --  Facebook  ------------------------------------------------------------ //
 
   // Can users use Facebook credentials to login to Phabricator?
   'facebook.auth-enabled'       => false,
 
   // Can users use Facebook credentials to create new Phabricator accounts?
   'facebook.registration-enabled' => true,
 
   // Are Facebook accounts permanently linked to Phabricator accounts, or can
   // the user unlink them?
   'facebook.auth-permanent'     => false,
 
   // The Facebook "Application ID" to use for Facebook API access.
   'facebook.application-id'     => null,
 
   // The Facebook "Application Secret" to use for Facebook API access.
   'facebook.application-secret' => null,
 
 
 // -- Github ---------------------------------------------------------------- //
 
   // Can users use Github credentials to login to Phabricator?
   'github.auth-enabled'         => false,
 
   // Can users use Github credentials to create new Phabricator accounts?
   'github.registration-enabled' => true,
 
   // Are Github accounts permanently linked to Phabricator accounts, or can
   // the user unlink them?
   'github.auth-permanent'       => false,
 
   // The Github "Client ID" to use for Github API access.
   'github.application-id'       => null,
 
   // The Github "Secret" to use for Github API access.
   'github.application-secret'   => null,
 
 
 // -- Recaptcha ------------------------------------------------------------- //
 
   // Is Recaptcha enabled? If disabled, captchas will not appear.
   'recaptcha.enabled'           => false,
 
   // Your Recaptcha public key, obtained from Recaptcha.
   'recaptcha.public-key'        => null,
 
   // Your Recaptcha private key, obtained from Recaptcha.
   'recaptcha.private-key'       => null,
 
 
 // -- Misc ------------------------------------------------------------------ //
 
   // This is hashed with other inputs to generate CSRF tokens. If you want, you
   // can change it to some other string which is unique to your install. This
   // will make your install more secure in a vague, mostly theoretical way. But
   // it will take you like 3 seconds of mashing on your keyboard to set it up so
   // you might as well.
   'phabricator.csrf-key'        => '0b7ec0592e0a2829d8b71df2fa269b2c6172eca3',
 
   // This is hashed with other inputs to generate mail tokens. If you want, you
   // can change it to some other string which is unique to your install. In
   // particular, you will want to do this if you accidentally send a bunch of
   // mail somewhere you shouldn't have, to invalidate all old reply-to
   // addresses.
   'phabricator.mail-key'        => '5ce3e7e8787f6e40dfae861da315a5cdf1018f12',
 
   // Version string displayed in the footer. You probably should leave this
   // alone.
   'phabricator.version'         => 'UNSTABLE',
 
   // PHP requires that you set a timezone in your php.ini before using date
   // functions, or it will emit a warning. If this isn't possible (for instance,
   // because you are using HPHP) you can set some valid constant for
   // date_default_timezone_set() here and Phabricator will set it on your
   // behalf, silencing the warning.
   'phabricator.timezone'        => null,
 
 
   // Phabricator can highlight PHP by default, but if you want syntax
   // highlighting for other languages you should install the python package
   // 'Pygments', make sure the 'pygmentize' script is available in the
   // $PATH of the webserver, and then enable this.
   'pygments.enabled'            => false,
 
 
 // -- Files ----------------------------------------------------------------- //
 
   // Lists which uploaded file types may be viewed in the browser. If a file
   // has a mime type which does not appear in this list, it will always be
   // downloaded instead of displayed. This is a security consideration: if a
   // user uploads a file of type "text/html" and it is displayed as
   // "text/html", they can eaily execute XSS attacks. This is also a usability
   // consideration, since browsers tend to freak out when viewing enormous
   // binary files.
   //
   // The keys in this array are viewable mime types; the values are the mime
   // types they will be delivered as when they are viewed in the browser.
   'files.viewable-mime-types' => array(
     'image/jpeg'  => 'image/jpeg',
     'image/jpg'   => 'image/jpg',
     'image/png'   => 'image/png',
     'image/gif'   => 'image/gif',
     'text/plain'  => 'text/plain; charset=utf-8',
   ),
 
   // Phabricator can proxy images from other servers so you can paste the URI
   // to a funny picture of a cat into the comment box and have it show up as an
   // image. However, this means the webserver Phabricator is running on will
   // make HTTP requests to arbitrary URIs. If the server has access to internal
   // resources, this could be a security risk. You should only enable it if you
   // are installed entirely a VPN and VPN access is required to access
   // Phabricator, or if the webserver has no special access to anything. If
   // unsure, it is safer to leave this disabled.
   'files.enable-proxy' => false,
 
 // -- Differential ---------------------------------------------------------- //
 
   'differential.revision-custom-detail-renderer'  => null,
 
 
 // -- Maniphest ------------------------------------------------------------- //
 
   'maniphest.enabled' => true,
 
 // -- Customization --------------------------------------------------------- //
 
   // Paths to additional phutil libraries to load.
   'load-libraries' => array(),
 
   'aphront.default-application-configuration-class' =>
     'AphrontDefaultApplicationConfiguration',
 
   'controller.oauth-registration' =>
     'PhabricatorOAuthDefaultRegistrationController',
 
 
   // Directory that phd (the Phabricator daemon control script) should use to
   // track running daemons.
   'phd.pid-directory' => '/var/tmp/phd',
 
   // This value is an input to the hash function when building resource hashes.
   // It has no security value, but if you accidentally poison user caches (by
   // pushing a bad patch or having something go wrong with a CDN, e.g.) you can
   // change this to something else and rebuild the Celerity map to break user
   // caches. Unless you are doing Celerity development, it is exceptionally
   // unlikely that you need to modify this.
   'celerity.resource-hash' => 'd9455ea150622ee044f7931dabfa52aa',
 
   // In a development environment, it is desirable to force static resources
   // (CSS and JS) to be read from disk on every request, so that edits to them
   // appear when you reload the page even if you haven't updated the resource
   // maps. This setting ensures requests will be verified against the state on
   // disk. Generally, you should leave this off in production (caching behavior
   // and performance improve with it off) but turn it on in development. (These
   // settings are the defaults.)
   'celerity.force-disk-reads' => false,
 
 );
diff --git a/src/applications/differential/mail/base/DifferentialMail.php b/src/applications/differential/mail/base/DifferentialMail.php
index 0fb82a5211..b497266f42 100644
--- a/src/applications/differential/mail/base/DifferentialMail.php
+++ b/src/applications/differential/mail/base/DifferentialMail.php
@@ -1,313 +1,315 @@
 <?php
 
 /*
  * Copyright 2011 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *   http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 
 abstract class DifferentialMail {
 
-  const SUBJECT_PREFIX  = '[Differential]';
-
   protected $to = array();
   protected $cc = array();
 
   protected $actorHandle;
 
   protected $revision;
   protected $comment;
   protected $changesets;
   protected $inlineComments;
   protected $isFirstMailAboutRevision;
   protected $isFirstMailToRecipients;
   protected $heraldTranscriptURI;
   protected $heraldRulesHeader;
   protected $replyHandler;
 
   abstract protected function renderSubject();
   abstract protected function renderBody();
 
   public function setActorHandle($actor_handle) {
     $this->actorHandle = $actor_handle;
     return $this;
   }
 
   public function getActorHandle() {
     return $this->actorHandle;
   }
 
   protected function getActorName() {
     $handle = $this->getActorHandle();
     if ($handle) {
       return $handle->getName();
     }
     return '???';
   }
 
   public function setXHeraldRulesHeader($header) {
     $this->heraldRulesHeader = $header;
     return $this;
   }
 
   public function send() {
     $to_phids = $this->getToPHIDs();
     if (!$to_phids) {
       throw new Exception('No "To:" users provided!');
     }
 
     $cc_phids = $this->getCCPHIDs();
     $subject  = $this->buildSubject();
     $body     = $this->buildBody();
 
     $template = new PhabricatorMetaMTAMail();
     $actor_handle = $this->getActorHandle();
     $reply_handler = $this->getReplyHandler();
 
     if ($actor_handle) {
       $template->setFrom($actor_handle->getPHID());
     }
 
     $template
       ->setSubject($subject)
       ->setBody($body)
       ->setIsHTML($this->shouldMarkMailAsHTML())
       ->addHeader('Thread-Topic', $this->getRevision()->getTitle());
 
     $template->setThreadID(
       $this->getThreadID(),
       $this->isFirstMailAboutRevision());
 
     if ($this->heraldRulesHeader) {
       $template->addHeader('X-Herald-Rules', $this->heraldRulesHeader);
     }
 
     $template->setRelatedPHID($this->getRevision()->getPHID());
 
     $phids = array();
     foreach ($to_phids as $phid) {
       $phids[$phid] = true;
     }
     foreach ($cc_phids as $phid) {
       $phids[$phid] = true;
     }
     $phids = array_keys($phids);
 
     $handles = id(new PhabricatorObjectHandleData($phids))->loadHandles();
 
     $mails = $reply_handler->multiplexMail(
       $template,
       array_select_keys($handles, $to_phids),
       array_select_keys($handles, $cc_phids));
 
     foreach ($mails as $mail) {
       $mail->saveAndSend();
     }
   }
 
+  protected function getSubjectPrefix() {
+    return PhabricatorEnv::getEnvConfig('metamta.differential.subject-prefix');
+  }
+
   protected function buildSubject() {
-    return self::SUBJECT_PREFIX.' '.$this->renderSubject();
+    return trim($this->getSubjectPrefix().' '.$this->renderSubject());
   }
 
   protected function shouldMarkMailAsHTML() {
     return false;
   }
 
   protected function buildBody() {
 
     $body = $this->renderBody();
 
     $reply_handler = $this->getReplyHandler();
     $reply_instructions = $reply_handler->getReplyHandlerInstructions();
     if ($reply_instructions) {
       $body .=
         "\nREPLY HANDLER ACTIONS\n".
         "  {$reply_instructions}\n";
     }
 
     if ($this->getHeraldTranscriptURI() && $this->isFirstMailToRecipients()) {
       $manage_uri = PhabricatorEnv::getProductionURI(
         '/herald/view/differential/');
 
       $xscript_uri = $this->getHeraldTranscriptURI();
       $body .= <<<EOTEXT
 
 MANAGE HERALD DIFFERENTIAL RULES
   {$manage_uri}
 
 WHY DID I GET THIS EMAIL?
   {$xscript_uri}
 
 Tip: use the X-Herald-Rules header to filter Herald messages in your client.
 
 EOTEXT;
     }
 
     return $body;
   }
 
   public function getReplyHandler() {
     if ($this->replyHandler) {
       return $this->replyHandler;
     }
 
     $handler_class = PhabricatorEnv::getEnvConfig(
       'metamta.differential.reply-handler');
 
     $reply_handler = self::newReplyHandlerForRevision($this->getRevision());
 
     $this->replyHandler = $reply_handler;
 
     return $this->replyHandler;
   }
 
   public static function newReplyHandlerForRevision(
     DifferentialRevision $revision) {
 
     $handler_class = PhabricatorEnv::getEnvConfig(
       'metamta.differential.reply-handler');
 
     $reply_handler = newv($handler_class, array());
     $reply_handler->setMailReceiver($revision);
 
     return $reply_handler;
   }
 
 
   protected function formatText($text) {
     $text = explode("\n", $text);
     foreach ($text as &$line) {
       $line = rtrim('  '.$line);
     }
     unset($line);
     return implode("\n", $text);
   }
 
   public function setToPHIDs(array $to) {
     $this->to = $this->filterContactPHIDs($to);
     return $this;
   }
 
   public function setCCPHIDs(array $cc) {
     $this->cc = $this->filterContactPHIDs($cc);
     return $this;
   }
 
   protected function filterContactPHIDs(array $phids) {
     return $phids;
 
     // TODO: actually do this?
 
     // Differential revisions use Subscriptions for CCs, so any arbitrary
     // PHID can end up CC'd to them. Only try to actually send email PHIDs
     // which have ToolsHandle types that are marked emailable. If we don't
     // filter here, sending the email will fail.
 /*
     $handles = array();
     prep(new ToolsHandleData($phids, $handles));
     foreach ($handles as $phid => $handle) {
       if (!$handle->isEmailable()) {
         unset($handles[$phid]);
       }
     }
     return array_keys($handles);
 */
   }
 
   protected function getToPHIDs() {
     return $this->to;
   }
 
   protected function getCCPHIDs() {
     return $this->cc;
   }
 
   public function setRevision($revision) {
     $this->revision = $revision;
     return $this;
   }
 
   public function getRevision() {
     return $this->revision;
   }
 
   protected function getThreadID() {
     $phid = $this->getRevision()->getPHID();
     $domain = PhabricatorEnv::getEnvConfig('metamta.domain');
     return "<differential-rev-{$phid}-req@{$domain}>";
   }
 
   public function setComment($comment) {
     $this->comment = $comment;
     return $this;
   }
 
   public function getComment() {
     return $this->comment;
   }
 
   public function setChangesets($changesets) {
     $this->changesets = $changesets;
     return $this;
   }
 
   public function getChangesets() {
     return $this->changesets;
   }
 
   public function setInlineComments(array $inline_comments) {
     $this->inlineComments = $inline_comments;
     return $this;
   }
 
   public function getInlineComments() {
     return $this->inlineComments;
   }
 
   public function renderRevisionDetailLink() {
     $uri = $this->getRevisionURI();
     return "REVISION DETAIL\n  {$uri}";
   }
 
   public function getRevisionURI() {
     return PhabricatorEnv::getProductionURI('/D'.$this->getRevision()->getID());
   }
 
   public function setIsFirstMailToRecipients($first) {
     $this->isFirstMailToRecipients = $first;
     return $this;
   }
 
   public function isFirstMailToRecipients() {
     return $this->isFirstMailToRecipients;
   }
 
   public function setIsFirstMailAboutRevision($first) {
     $this->isFirstMailAboutRevision = $first;
     return $this;
   }
 
   public function isFirstMailAboutRevision() {
     return $this->isFirstMailAboutRevision;
   }
 
   public function setHeraldTranscriptURI($herald_transcript_uri) {
     $this->heraldTranscriptURI = $herald_transcript_uri;
     return $this;
   }
 
   public function getHeraldTranscriptURI() {
     return $this->heraldTranscriptURI;
   }
 
 }
diff --git a/src/applications/differential/mail/newdiff/DifferentialNewDiffMail.php b/src/applications/differential/mail/newdiff/DifferentialNewDiffMail.php
index 1507011844..9b18f6fd67 100644
--- a/src/applications/differential/mail/newdiff/DifferentialNewDiffMail.php
+++ b/src/applications/differential/mail/newdiff/DifferentialNewDiffMail.php
@@ -1,68 +1,67 @@
 <?php
 
 /*
  * Copyright 2011 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *   http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 
 class DifferentialNewDiffMail extends DifferentialReviewRequestMail {
 
   protected function renderSubject() {
     $revision = $this->getRevision();
     $line_count = $revision->getLineCount();
     $lines = ($line_count == 1 ? "1 line" : "{$line_count} lines");
 
     if ($this->isFirstMailToRecipients()) {
       $verb = 'Request';
     } else {
       $verb = 'Updated';
     }
 
     $revision_id = $revision->getID();
     $revision_title = $revision->getTitle();
 
     return "[{$verb}, {$lines}] D{$revision_id}: {$revision_title}";
   }
 
   protected function buildSubject() {
     if (!$this->isFirstMailToRecipients()) {
       return parent::buildSubject();
     }
 
-    $prefix = self::SUBJECT_PREFIX;
-
+    $prefix = $this->getSubjectPrefix();
     $subject = $this->renderSubject();
 
-    return "{$prefix} {$subject}";
+    return trim("{$prefix} {$subject}");
   }
 
   protected function renderBody() {
     $actor = $this->getActorName();
 
     $name  = $this->getRevision()->getTitle();
 
     $body = array();
 
     if ($this->isFirstMailToRecipients()) {
       $body[] = "{$actor} requested code review of \"{$name}\".";
     } else {
       $body[] = "{$actor} updated the revision \"{$name}\".";
     }
     $body[] = null;
 
     $body[] = $this->renderReviewRequestBody();
 
     return implode("\n", $body);
   }
 }
diff --git a/src/applications/maniphest/editor/transaction/ManiphestTransactionEditor.php b/src/applications/maniphest/editor/transaction/ManiphestTransactionEditor.php
index de6af55571..75067cd628 100644
--- a/src/applications/maniphest/editor/transaction/ManiphestTransactionEditor.php
+++ b/src/applications/maniphest/editor/transaction/ManiphestTransactionEditor.php
@@ -1,224 +1,229 @@
 <?php
 
 /*
  * Copyright 2011 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *   http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 
 class ManiphestTransactionEditor {
-  const SUBJECT_PREFIX = '[Maniphest]';
 
   public function applyTransactions($task, array $transactions) {
 
     $email_cc = $task->getCCPHIDs();
 
     $email_to = array();
     $email_to[] = $task->getOwnerPHID();
 
     foreach ($transactions as $key => $transaction) {
       $type = $transaction->getTransactionType();
       $new = $transaction->getNewValue();
       $email_to[] = $transaction->getAuthorPHID();
 
       switch ($type) {
         case ManiphestTransactionType::TYPE_NONE:
           $old = null;
           break;
         case ManiphestTransactionType::TYPE_STATUS:
           $old = $task->getStatus();
           break;
         case ManiphestTransactionType::TYPE_OWNER:
           $old = $task->getOwnerPHID();
           break;
         case ManiphestTransactionType::TYPE_CCS:
           $old = $task->getCCPHIDs();
           break;
         case ManiphestTransactionType::TYPE_PRIORITY:
           $old = $task->getPriority();
           break;
         case ManiphestTransactionType::TYPE_ATTACH:
           $old = $task->getAttached();
           break;
         case ManiphestTransactionType::TYPE_TITLE:
           $old = $task->getTitle();
           break;
         case ManiphestTransactionType::TYPE_DESCRIPTION:
           $old = $task->getDescription();
           break;
         case ManiphestTransactionType::TYPE_PROJECTS:
           $old = $task->getProjectPHIDs();
           break;
         default:
           throw new Exception('Unknown action type.');
       }
 
       if (($old !== null) && ($old == $new)) {
         if (count($transactions) > 1 && !$transaction->hasComments()) {
           // If we have at least one other transaction and this one isn't
           // doing anything and doesn't have any comments, just throw it
           // away.
           unset($transactions[$key]);
           continue;
         } else {
           $transaction->setOldValue(null);
           $transaction->setNewValue(null);
           $transaction->setTransactionType(ManiphestTransactionType::TYPE_NONE);
         }
       } else {
         switch ($type) {
           case ManiphestTransactionType::TYPE_NONE:
             break;
           case ManiphestTransactionType::TYPE_STATUS:
             $task->setStatus($new);
             break;
           case ManiphestTransactionType::TYPE_OWNER:
             $task->setOwnerPHID($new);
             break;
           case ManiphestTransactionType::TYPE_CCS:
             $task->setCCPHIDs($new);
             break;
           case ManiphestTransactionType::TYPE_PRIORITY:
             $task->setPriority($new);
             break;
           case ManiphestTransactionType::TYPE_ATTACH:
             $task->setAttached($new);
             break;
           case ManiphestTransactionType::TYPE_TITLE:
             $task->setTitle($new);
             break;
           case ManiphestTransactionType::TYPE_DESCRIPTION:
             $task->setDescription($new);
             break;
           case ManiphestTransactionType::TYPE_PROJECTS:
             $task->setProjectPHIDs($new);
             break;
           default:
             throw new Exception('Unknown action type.');
         }
 
         $transaction->setOldValue($old);
         $transaction->setNewValue($new);
       }
 
     }
 
     $task->save();
     foreach ($transactions as $transaction) {
       $transaction->setTaskID($task->getID());
       $transaction->save();
     }
 
     $email_to[] = $task->getOwnerPHID();
     $email_cc = array_merge(
       $email_cc,
       $task->getCCPHIDs());
 
     // TODO: Do this offline via timeline
     PhabricatorSearchManiphestIndexer::indexTask($task);
 
     $this->sendEmail($task, $transactions, $email_to, $email_cc);
   }
 
+  protected function getSubjectPrefix() {
+    return PhabricatorEnv::getEnvConfig('metamta.maniphest.subject-prefix');
+  }
+
   private function sendEmail($task, $transactions, $email_to, $email_cc) {
     $email_to = array_filter(array_unique($email_to));
     $email_cc = array_filter(array_unique($email_cc));
 
     $phids = array();
     foreach ($transactions as $transaction) {
       foreach ($transaction->extractPHIDs() as $phid) {
         $phids[$phid] = true;
       }
     }
     foreach ($email_to as $phid) {
       $phids[$phid] = true;
     }
     foreach ($email_cc as $phid) {
       $phids[$phid] = true;
     }
     $phids = array_keys($phids);
 
     $handles = id(new PhabricatorObjectHandleData($phids))
       ->loadHandles();
 
     $view = new ManiphestTransactionDetailView();
     $view->setTransactionGroup($transactions);
     $view->setHandles($handles);
     list($action, $body) = $view->renderForEmail($with_date = false);
 
     $is_create = false;
     foreach ($transactions as $transaction) {
       $type = $transaction->getTransactionType();
       if (($type == ManiphestTransactionType::TYPE_STATUS) &&
           ($transaction->getOldValue() === null) &&
           ($transaction->getNewValue() == ManiphestTaskStatus::STATUS_OPEN)) {
         $is_create = true;
       }
     }
 
     $task_uri = PhabricatorEnv::getURI('/T'.$task->getID());
 
     $reply_handler = $this->buildReplyHandler($task);
 
     if ($is_create) {
       $body .=
         "\n\n".
         "TASK DESCRIPTION\n".
         "  ".$task->getDescription();
     }
 
     $body .=
       "\n\n".
       "TASK DETAIL\n".
       "  ".$task_uri."\n";
 
     $reply_instructions = $reply_handler->getReplyHandlerInstructions();
     if ($reply_instructions) {
       $body .=
         "\n".
         "REPLY HANDLER ACTIONS\n".
         "  ".$reply_instructions."\n";
     }
 
     $thread_id = '<maniphest-task-'.$task->getPHID().'>';
     $task_id = $task->getID();
     $title = $task->getTitle();
+    $prefix = $this->getSubjectPrefix();
+    $subject = trim("{$prefix} [{$action}] T{$task_id}: {$title}");
 
     $template = id(new PhabricatorMetaMTAMail())
-      ->setSubject(self::SUBJECT_PREFIX." [{$action}] T{$task_id}: {$title}")
+      ->setSubject($subject)
       ->setFrom($transaction->getAuthorPHID())
       ->addHeader('Thread-Topic', 'Maniphest Task '.$task->getID())
       ->setThreadID($thread_id, $is_create)
       ->setRelatedPHID($task->getPHID())
       ->setBody($body);
 
     $mails = $reply_handler->multiplexMail(
       $template,
       array_select_keys($handles, $email_to),
       array_select_keys($handles, $email_cc));
 
     foreach ($mails as $mail) {
       $mail->saveAndSend();
     }
   }
 
   public function buildReplyHandler(ManiphestTask $task) {
     $handler_class = PhabricatorEnv::getEnvConfig(
       'metamta.maniphest.reply-handler');
 
     $handler_object = newv($handler_class, array());
     $handler_object->setMailReceiver($task);
 
     return $handler_object;
   }
 }