Got report after upgrade to Debian Jessie that SquirrelMail does not show messages using quoted-printable.

http://sourceforge.net/p/squirrelmail/bugs/2806/

--- /usr/share/squirrelmail/functions/i18n.php.orig	2015-09-16 02:31:36.763732202 +0200
+++ /usr/share/squirrelmail/functions/i18n.php	2015-09-16 02:34:27.983563079 +0200
@@ -184,7 +184,7 @@
     }
 
     /* All HTML special characters are 7 bit and can be replaced first */
-    if (! $save_html) $string = sm_encode_html_special_chars ($string);
+    if (! $save_html) $string = sm_encode_html_special_chars($string, ENT_COMPAT, $charset);
     $charset = strtolower($charset);
 
     set_my_charset();
--- /usr/share/squirrelmail/functions/strings.php.orig	2015-09-16 02:34:52.320107664 +0200
+++ /usr/share/squirrelmail/functions/strings.php	2015-09-16 02:36:26.822222562 +0200
@@ -1496,6 +1496,24 @@
 function sm_encode_html_special_chars($string, $flags=ENT_COMPAT,
                                       $encoding=NULL, $double_encode=TRUE)
 {
+
+   static $htmlspecialchars_charsets = array(
+      'iso-8859-1', 'iso8859-1',
+      'iso-8859-5', 'iso8859-5',
+      'iso-8859-15', 'iso8859-15',
+      'utf-8',
+      'cp866', 'ibm866', '866',
+      'cp1251', 'windows-1251', 'win-1251', '1251',
+      'cp1252', 'windows-1252', '1252',
+      'koi8-R', 'koi8-ru', 'koi8r',
+      'big5', '950',
+      'gb2312', '936',
+      'big5-hkscs',
+      'shift_jis', 'sjis', 'sjis-win', 'cp932', '932',
+      'euc-jp', 'eucjp', 'eucjp-win',
+      'macroman',
+   );
+
    if (!$encoding)
    {
       global $default_charset;
@@ -1504,6 +1522,17 @@
       $encoding = $default_charset;
    }
 
+   if (!in_array(strtolower($encoding), $htmlspecialchars_charsets))
+   {
+      // use default from configuration if provided or hard-coded fallback
+      //
+      global $default_htmlspecialchars_encoding;
+      if (!empty($default_htmlspecialchars_encoding))
+         $encoding = $default_htmlspecialchars_encoding;
+      else
+         $encoding = 'iso-8859-1';
+   }
+
    if (check_php_version(5, 2, 3))
       return htmlspecialchars($string, $flags, $encoding, $double_encode);

No idea what it does and if this is ever going to be mainlined.