Gets the charset of the MIME part.
The string containing the charset of the MIME part contents, or a null reference (Nothing in Visual Basic) if no charset information is available.
Examples: "us-ascii", "ISO-8859-1", "gb2312", "shift-jis", "Windows-1252".
MailBee obtains the charset from the value of "charset" parameter of BodyParams.
ImapBodyStructure Class | MailBee.ImapMail Namespace