See here
Hello I had same problems. I have found the solution in Forum
edit //include/pear/Mail/mime.php, and replace ISO-8859-1 by UTF-8 around line 187
Code:
'html_charset' => 'UTF-8',
'text_charset' => 'UTF-8',
'head_charset' => 'UTF-8'
http://www.osticket.com/forums/showthread.php?t=1152(http://www.osticket.com/forums/showthread.php?t=1152)
See here (Buraya bakınız:)