(string) With this option, the SMSC’s default character set may be specified. Use the character set names given in the file
When this option is not specified, then US-ASCII is assumed. Note that the mnemonic names used in charsets.txt are defined in charnames.txt in the same directory.
When processing an email message, the header lines and text message parts are first decoded and then converted to Unicode. Next, the data is then converted to either the SMSC’s default character set or UCS2, depending on the value of the USE_UCS2 option and whether or not the SMS message contains at least one glyph not found in the default SMSC character set. Note that the UCS2 character set is a 16-bit encoding of Unicode and is often referred to as UTF-16.