diff --git a/SECURITY b/SECURITY.md
similarity index 100%
rename from SECURITY
rename to SECURITY.md
diff --git a/class.phpmailer.php b/class.phpmailer.php
index 1136c9546..dabb68e99 100644
--- a/class.phpmailer.php
+++ b/class.phpmailer.php
@@ -1683,7 +1683,11 @@ public function setLanguage($langcode = 'en', $lang_path = '')
     {
         // Backwards compatibility for renamed language codes
         $renamed_langcodes = array(
+            'br' => 'pt_br',
+            'cz' => 'cs',
             'dk' => 'da',
+            'no' => 'nb',
+            'se' => 'sv',
         );
 
         if (isset($renamed_langcodes[$langcode])) {
diff --git a/docs/Note_for_SMTP_debugging.md b/docs/Note_for_SMTP_debugging.md
new file mode 100644
index 000000000..b89a7d159
--- /dev/null
+++ b/docs/Note_for_SMTP_debugging.md
@@ -0,0 +1,44 @@
+#SMTP Debugging
+
+If you are having problems connecting or sending emails through your SMTP server, the SMTP class can provide more information about the processing/errors taking place.
+Use the debug functionality of the class to see what's going on in your connections. To do that, set the debug level in your script. For example:
+
+```php
+$mail->SMTPDebug = 2;
+$mail->isSMTP();  // tell the class to use SMTP
+$mail->SMTPAuth   = true;                // enable SMTP authentication
+$mail->Port       = 25;                  // set the SMTP port
+$mail->Host       = "mail.yourhost.com"; // SMTP server
+$mail->Username   = "name@yourhost.com"; // SMTP account username
+$mail->Password   = "your password";     // SMTP account password
+```
+
+##Debug levels
+
+Setting the `SMTPDebug` property results in different amounts of output:
+
+ * `0`: Disable debugging (you can also leave this out completely, 0 is the default).
+ * `1`: Output messages sent by the client.
+ * `2`: as 1, plus responses received from the server (this is probably the most useful setting for debugging).
+ * `3`: as 2, plus more information about the initial connection.
+ * `4`: as 3, plus even lower-level information, very verbose.
+
+You don't need to use levels above 2 unless you're having trouble connecting at all - it will just make output more verbose and more difficult to read.
+
+Note that you will get no output until you call `send()`, because no SMTP conversation takes place until you do that.
+
+##Debug output format
+
+The form that the debug output taks is determined by the `Debugoutput` property. This has several options:
+
+ * `echo` Output plain-text as-is, appropriate for CLI
+ * `html` Output escaped, line breaks converted to `<br>`, appropriate for browser output
+ * `error_log` Output to error log as configured in php.ini
+
+By default PHPMailer will use `echo` if run from a `cli` or `cli-server` SAPI, `html` otherwise. Alternatively, you can implement your own system by providing a callable expecting two parameters: a message string and the debug level:
+
+    $mail->Debugoutput = function($str, $level) {echo "debug level $level; message: $str";};
+
+You can of course make this more complex - for example your could capture all the output and store it in a database.
+
+And finally, don't forget to disable debugging before going into production.
diff --git a/docs/Note_for_SMTP_debugging.txt b/docs/Note_for_SMTP_debugging.txt
deleted file mode 100644
index 128b2d9d8..000000000
--- a/docs/Note_for_SMTP_debugging.txt
+++ /dev/null
@@ -1,17 +0,0 @@
-If you are having problems connecting or sending emails through your SMTP server, the SMTP class can provide more information about the processing/errors taking place.
-Use the debug functionality of the class to see what's going on in your connections. To do that, set the debug level in your script. For example:
-
-$mail->SMTPDebug = 1;
-$mail->isSMTP();  // telling the class to use SMTP
-$mail->SMTPAuth   = true;                // enable SMTP authentication
-$mail->Port       = 26;                  // set the SMTP port
-$mail->Host       = "mail.yourhost.com"; // SMTP server
-$mail->Username   = "name@yourhost.com"; // SMTP account username
-$mail->Password   = "your password";     // SMTP account password
-
-Notes on this:
-$mail->SMTPDebug = 0; ... will disable debugging (you can also leave this out completely, 0 is the default)
-$mail->SMTPDebug = 1; ... will echo errors and server responses
-$mail->SMTPDebug = 2; ... will echo errors, server responses and client messages
-
-And finally, don't forget to disable debugging before going into production.
diff --git a/language/phpmailer.lang-cz.php b/language/phpmailer.lang-cs.php
similarity index 100%
rename from language/phpmailer.lang-cz.php
rename to language/phpmailer.lang-cs.php
diff --git a/language/phpmailer.lang-no.php b/language/phpmailer.lang-nb.php
similarity index 100%
rename from language/phpmailer.lang-no.php
rename to language/phpmailer.lang-nb.php
diff --git a/language/phpmailer.lang-br.php b/language/phpmailer.lang-pt_br.php
similarity index 100%
rename from language/phpmailer.lang-br.php
rename to language/phpmailer.lang-pt_br.php
diff --git a/language/phpmailer.lang-se.php b/language/phpmailer.lang-sv.php
similarity index 100%
rename from language/phpmailer.lang-se.php
rename to language/phpmailer.lang-sv.php