diff --git a/root/usr/share/mozilla-mcd/firefox.php b/root/usr/share/mozilla-mcd/firefox.php
index 93aad45..16e568b 100644
--- a/root/usr/share/mozilla-mcd/firefox.php
+++ b/root/usr/share/mozilla-mcd/firefox.php
@@ -17,8 +17,13 @@ if(isset($_SERVER['QUERY_STRING']) && preg_match('/^.+@' . DOMAIN . '$/', $_SERV
     $result = ldap_search($link, USER_BASE, "uid=" . $uid);
     $user = ldap_get_entries($link, $result);
     if($user['count'] == 0) {
-        // user not found
-        exit;
+        // Search for the mail address
+        $result = ldap_search($link, USER_BASE, "mail=" . $_SERVER['QUERY_STRING']);
+        $user = ldap_get_entries($link, $result);
+        if($user['count'] != 1) {
+            // user not found or multiple result found
+            exit;
+        }
     }
     $pref = FF_PREF;
     // Don't lock pref if the user is member of some special groups
diff --git a/root/usr/share/mozilla-mcd/thunderbird.php b/root/usr/share/mozilla-mcd/thunderbird.php
index 3b15086..1bb6276 100644
--- a/root/usr/share/mozilla-mcd/thunderbird.php
+++ b/root/usr/share/mozilla-mcd/thunderbird.php
@@ -16,8 +16,13 @@ if(isset($_SERVER['QUERY_STRING']) && preg_match('/^.+@' . DOMAIN . '$/', $_SERV
     $result = ldap_search($link, USER_BASE, "uid=" . $uid);
     $user = ldap_get_entries($link, $result);
     if($user['count'] == 0) {
-        // user not found
-        exit;
+        // Search for the mail address
+        $result = ldap_search($link, USER_BASE, "mail=" . $_SERVER['QUERY_STRING']);
+        $user = ldap_get_entries($link, $result);
+        if($user['count'] != 1) {
+            // user not found or multiple result found
+            exit;
+        }
     }
     $pref = TB_PREF;
     // Don't lock pref if the user is member of some special groups