JavaMail automatically encodes the e-mail message parts before sending an e-mail and after receiving it, decodes the message while reading it. The MIME specification does not allow header parameter values such as attachment’s file name to be encoded. That is why JavaMail does not encode or decode filenames in the header. Business Process Server’s EmailReader is configured to decode the filename in the order specified below:
Base64
QuotedPrintable
EmailReader uses JavaMail’s MimeUtility and Commons-Codec to decode the encoded file names.