swiftmailer error on a new server

I have an error when i mail from a new server . I pay you for 1hour work. I have others questions. and maybe if we have a good contact i can hire you for a more important work. thanks Uncaught exception 'RuntimeException' with message 'Charset "iso-8859-1" not supported. NativeQpContentEncoder only supports "utf-8"' in /var/www/vhosts/[login to view URL]:28 Stack trace: #0 /var/www/vhosts/[login to view URL](787): Swift_Mime_ContentEncoder_NativeQpContentEncoder->charsetChanged('iso-8859-1') #1 /var/www/vhosts/[login to view URL](449): Swift_Mime_SimpleMimeEntity->_notifyCharsetChanged('iso-8859-1') #2 /var/www/vhosts/[login to view URL](96): Swift_Mime_SimpleMimeEntity->charsetChanged('iso-8859-1') #3 /var/www/vhosts/[login to view URL](46): Swift_Mime_MimePart->setCharset('iso-8859-1') #4 /var/www/vhosts/[login to view URL](31): Swi in <b>/var/www/vhosts/[login to view URL]</b> on line <b>28</b><br />