diff --git a/plugins/kolab_addressbook/lib/rcube_kolab_contacts.php b/plugins/kolab_addressbook/lib/rcube_kolab_contacts.php
index 782c06b3..5b897c27 100644
--- a/plugins/kolab_addressbook/lib/rcube_kolab_contacts.php
+++ b/plugins/kolab_addressbook/lib/rcube_kolab_contacts.php
@@ -896,6 +896,31 @@ class rcube_kolab_contacts extends rcube_addressbook
         return false;
     }
 
+    /**
+     * Check the given data before saving.
+     * If input not valid, the message to display can be fetched using get_error()
+     *
+     * @param array Associative array with contact data to save
+     *
+     * @return boolean True if input is valid, False if not.
+     */
+    public function validate($save_data)
+    {
+        // validate e-mail addresses
+        $valid = parent::validate($save_data);
+
+        // require at least one e-mail address (syntax check is already done)
+        if ($valid) {
+            if (!strlen($save_data['name'])
+                && !array_filter($this->get_col_values('email', $save_data, true))
+            ) {
+                $this->set_error('warning', 'kolab_addressbook.noemailnamewarning');
+                $valid = false;
+            }
+        }
+
+        return $valid;
+    }
 
     /**
      * Establishes a connection to the Kolab_Data object for accessing contact data
@@ -907,7 +932,6 @@ class rcube_kolab_contacts extends rcube_addressbook
         }
     }
 
-
     /**
      * Establishes a connection to the Kolab_Data object for accessing groups data
      */
@@ -918,7 +942,6 @@ class rcube_kolab_contacts extends rcube_addressbook
         }
     }
 
-
     /**
      * Simply fetch all records and store them in private member vars
      */
@@ -945,7 +968,6 @@ class rcube_kolab_contacts extends rcube_addressbook
         }
     }
 
-
     /**
      * Callback function for sorting contacts
      */
@@ -954,7 +976,6 @@ class rcube_kolab_contacts extends rcube_addressbook
       return strcasecmp($a['name'], $b['name']);
     }
 
-
     /**
      * Read distribution-lists AKA groups from server
      */
@@ -979,7 +1000,6 @@ class rcube_kolab_contacts extends rcube_addressbook
         }
     }
 
-
     /**
      * Map fields from internal Kolab_Format to Roundcube contact format
      */
@@ -1030,6 +1050,9 @@ class rcube_kolab_contacts extends rcube_addressbook
         return array_filter($out);
     }
 
+    /**
+     * Map fields from Roundcube format to internal Kolab_Format
+     */
     private function _from_rcube_contact($contact)
     {
         $object = array();
diff --git a/plugins/kolab_addressbook/localization/en_US.inc b/plugins/kolab_addressbook/localization/en_US.inc
index ce90f60a..f3cb17ea 100644
--- a/plugins/kolab_addressbook/localization/en_US.inc
+++ b/plugins/kolab_addressbook/localization/en_US.inc
@@ -25,12 +25,13 @@ $labels['globalonly'] = 'Global address book(s) only';
 $messages['bookdeleteconfirm']  = 'Do you really want to delete the selected address book and all contacts in it?';
 $messages['bookdeleting'] = 'Deleting address book...';
 $messages['booksaving'] = 'Saving address book...';
-$messages['bookdeleted'] = 'Address book deleted successfully';
-$messages['bookupdated'] = 'Address book updated successfully';
-$messages['bookcreated'] = 'Address book created successfully';
-$messages['bookdeleteerror'] = 'An error occured while deleting address book';
-$messages['bookupdateerror'] = 'An error occured while updating address book';
-$messages['bookcreateerror'] = 'An error occured while creating address book';
-$messages['nobooknamewarning'] = 'Please, enter address book name';
+$messages['bookdeleted'] = 'Address book deleted successfully.';
+$messages['bookupdated'] = 'Address book updated successfully.';
+$messages['bookcreated'] = 'Address book created successfully.';
+$messages['bookdeleteerror'] = 'An error occured while deleting address book.';
+$messages['bookupdateerror'] = 'An error occured while updating address book.';
+$messages['bookcreateerror'] = 'An error occured while creating address book.';
+$messages['nobooknamewarning'] = 'Please, enter address book name.';
+$messages['noemailnamewarning'] = 'Please, enter email address or contact name.';
 
 ?>
diff --git a/plugins/kolab_addressbook/localization/pl_PL.inc b/plugins/kolab_addressbook/localization/pl_PL.inc
index 61887231..e2735783 100644
--- a/plugins/kolab_addressbook/localization/pl_PL.inc
+++ b/plugins/kolab_addressbook/localization/pl_PL.inc
@@ -25,12 +25,13 @@ $labels['parentbook'] = 'Książka nadrzędna';
 $messages['bookdeleteconfirm'] = 'Czy na pewno chcesz usunąć wybraną książkę i wszystkie kontakty w niej zapisane?';
 $messages['bookdeleting'] = 'Usuwanie książki adresowej...';
 $messages['booksaving'] = 'Zapisywanie książki adresowej...';
-$messages['bookdeleted'] = 'Książka adresowa została usunięta';
-$messages['bookupdated'] = 'Książka adresowa została zaktualizowana';
-$messages['bookcreated'] = 'Książka adresowa została utworzona';
-$messages['bookdeleteerror'] = 'Wystąpił błąd podczas usuwania książki adresowej';
-$messages['bookupdateerror'] = 'Wystąpił błąd podczas zmiany książki adresowej';
-$messages['bookcreateerror'] = 'Wystąpił błąd podczas tworzenia książki adresowej';
-$messages['nobooknamewarning'] = 'Proszę podać nazwę książki adresowej';
+$messages['bookdeleted'] = 'Książka adresowa została usunięta.';
+$messages['bookupdated'] = 'Książka adresowa została zaktualizowana.';
+$messages['bookcreated'] = 'Książka adresowa została utworzona.';
+$messages['bookdeleteerror'] = 'Wystąpił błąd podczas usuwania książki adresowej.';
+$messages['bookupdateerror'] = 'Wystąpił błąd podczas zmiany książki adresowej.';
+$messages['bookcreateerror'] = 'Wystąpił błąd podczas tworzenia książki adresowej.';
+$messages['nobooknamewarning'] = 'Proszę podać nazwę książki adresowej.';
+$messages['noemailnamewarning'] = 'Proszę podać adres email lub nazwę kontaktu.';
 
 ?>