diff --git a/CHANGELOG.md b/CHANGELOG.md
index a7bfc445..031801ef 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -29,7 +29,7 @@ Setup:
 * The system hostname is now set during setup.
 * A swap file is now created if system memory is less than 2GB, 5GB of free disk space is available, and if no swap file yet exists.
 * We now install Roundcube from the official GitHub repository instead of our own mirror, which we had previously created to solve problems with SourceForge.
-
+* DKIM was incorrectly set up on machines where "localhost" was defined as something other than "127.0.0.1".
 
 v0.17c (April 1, 2016)
 ----------------------
diff --git a/conf/zpush/backend_caldav.php b/conf/zpush/backend_caldav.php
index 7bddded9..b10ebc3e 100644
--- a/conf/zpush/backend_caldav.php
+++ b/conf/zpush/backend_caldav.php
@@ -6,7 +6,7 @@
 ************************************************/
 
 define('CALDAV_PROTOCOL', 'https');
-define('CALDAV_SERVER', 'localhost');
+define('CALDAV_SERVER', '127.0.0.1');
 define('CALDAV_PORT', '443');
 define('CALDAV_PATH', '/caldav/calendars/%u/');
 define('CALDAV_PERSONAL', 'PRINCIPAL');
diff --git a/conf/zpush/backend_carddav.php b/conf/zpush/backend_carddav.php
index edf32901..4b166ad5 100644
--- a/conf/zpush/backend_carddav.php
+++ b/conf/zpush/backend_carddav.php
@@ -7,7 +7,7 @@
 
 
 define('CARDDAV_PROTOCOL', 'https'); /* http or https */
-define('CARDDAV_SERVER', 'localhost');
+define('CARDDAV_SERVER', '127.0.0.1');
 define('CARDDAV_PORT', '443');
 define('CARDDAV_PATH', '/carddav/addressbooks/%u/');
 define('CARDDAV_DEFAULT_PATH', '/carddav/addressbooks/%u/contacts/'); /* subdirectory of the main path */
diff --git a/conf/zpush/backend_imap.php b/conf/zpush/backend_imap.php
index 3f69f53e..84dc7358 100644
--- a/conf/zpush/backend_imap.php
+++ b/conf/zpush/backend_imap.php
@@ -5,7 +5,7 @@
 * Descr     :   IMAP backend configuration file
 ************************************************/
 
-define('IMAP_SERVER', 'localhost');
+define('IMAP_SERVER', '127.0.0.1');
 define('IMAP_PORT', 993);
 define('IMAP_OPTIONS', '/ssl/norsh/novalidate-cert');
 define('IMAP_DEFAULTFROM', '');
@@ -44,7 +44,7 @@ define('IMAP_FROM_LDAP_FROM', '#givenname #sn <#mail>');
 define('IMAP_SMTP_METHOD', 'sendmail');
 
 global $imap_smtp_params;
-$imap_smtp_params = array('host' => 'ssl://localhost', 'port' => 587, 'auth' => true, 'username' => 'imap_username', 'password' => 'imap_password');
+$imap_smtp_params = array('host' => 'ssl://127.0.0.1', 'port' => 587, 'auth' => true, 'username' => 'imap_username', 'password' => 'imap_password');
 
 define('MAIL_MIMEPART_CRLF', "\r\n");
 
diff --git a/management/email_administrator.py b/management/email_administrator.py
index 84d27460..b16fda1d 100755
--- a/management/email_administrator.py
+++ b/management/email_administrator.py
@@ -33,7 +33,7 @@ msg['Subject'] = "[%s] %s" % (env['PRIMARY_HOSTNAME'], subject)
 msg.set_payload(content, "UTF-8")
 
 # send
-smtpclient = smtplib.SMTP('localhost', 25)
+smtpclient = smtplib.SMTP('127.0.0.1', 25)
 smtpclient.ehlo()
 smtpclient.sendmail(
         admin_addr, # MAIL FROM
diff --git a/setup/dkim.sh b/setup/dkim.sh
index ed56c765..830e9e18 100755
--- a/setup/dkim.sh
+++ b/setup/dkim.sh
@@ -31,7 +31,7 @@ ExternalIgnoreList      refile:/etc/opendkim/TrustedHosts
 InternalHosts           refile:/etc/opendkim/TrustedHosts
 KeyTable                refile:/etc/opendkim/KeyTable
 SigningTable            refile:/etc/opendkim/SigningTable
-Socket                  inet:8891@localhost
+Socket                  inet:8891@127.0.0.1
 RequireSafeKeys         false
 EOF
 fi
diff --git a/setup/owncloud.sh b/setup/owncloud.sh
index 94dd70b6..cc58a5ca 100755
--- a/setup/owncloud.sh
+++ b/setup/owncloud.sh
@@ -108,12 +108,12 @@ if [ ! -f $STORAGE_ROOT/owncloud/owncloud.db ]; then
   'user_backends' => array(
     array(
       'class'=>'OC_User_IMAP',
-      'arguments'=>array('{localhost:993/imap/ssl/novalidate-cert}')
+      'arguments'=>array('{127.0.0.1:993/imap/ssl/novalidate-cert}')
     )
   ),
   'memcache.local' => '\\OC\\Memcache\\Memcached',
   "memcached_servers" => array (
-    array('localhost', 11211),
+    array('127.0.0.1', 11211),
   ),
   'mail_smtpmode' => 'sendmail',
   'mail_smtpsecure' => '',
diff --git a/setup/start.sh b/setup/start.sh
index 09dc8956..9d19a411 100755
--- a/setup/start.sh
+++ b/setup/start.sh
@@ -112,7 +112,7 @@ source setup/management.sh
 source setup/munin.sh
 
 # Ping the management daemon to write the DNS and nginx configuration files.
-until nc -z -w 4 localhost 10222
+until nc -z -w 4 127.0.0.1 10222
 do
 	echo Waiting for the Mail-in-a-Box management daemon to start...
 	sleep 2
diff --git a/setup/webmail.sh b/setup/webmail.sh
index e6434555..a325b1c4 100755
--- a/setup/webmail.sh
+++ b/setup/webmail.sh
@@ -91,10 +91,10 @@ cat > /usr/local/lib/roundcubemail/config/config.inc.php <<EOF;
 \$config['log_dir'] = '/var/log/roundcubemail/';
 \$config['temp_dir'] = '/tmp/roundcubemail/';
 \$config['db_dsnw'] = 'sqlite:///$STORAGE_ROOT/mail/roundcube/roundcube.sqlite?mode=0640';
-\$config['default_host'] = 'ssl://localhost';
+\$config['default_host'] = 'ssl://127.0.0.1';
 \$config['default_port'] = 993;
 \$config['imap_timeout'] = 15;
-\$config['smtp_server'] = 'tls://localhost';
+\$config['smtp_server'] = 'tls://127.0.0.1';
 \$config['smtp_port'] = 587;
 \$config['smtp_user'] = '%u';
 \$config['smtp_pass'] = '%p';
@@ -121,7 +121,7 @@ cat > /usr/local/lib/roundcubemail/plugins/vacation_sieve/config.inc.php <<EOF;
     'transfer' => array(
         'mode' =>  'managesieve',
         'ms_activate_script' => true,
-        'host'   => 'localhost',
+        'host'   => '127.0.0.1',
         'port'   => '4190',
         'usetls' => false,
         'path' => 'vacation',