AltMessageBodyCharset indicates which character set should be used to display alternative body of the message. Default value of AltMessageBodyCharset property is an empty string. Most common values of AltMessageBodyCharset property are:
"us-ascii" - US ASCII
"iso-8859-1" - Western European (ISO)
"windows-1252" - Western European (Windows)
"unicode" - Unicode (internally converted to UTF-8)
"iso-8859-2" - Central European (ISO)
"windows-1250" - Central European (Windows)