bsfilter 1:1.0.19-4 (riscv64 binary) in ubuntu lunar

 Bsfilter is a spam filter which can distinguish spam mail from other mails.
 It can read mails by three way:
   * reads from normal file or stdin.
   * retrieves and stores from IMAP server.
   * reads from POP server and passes to POP client. (POP proxy)
 Bsfilter gives nice support of Japanese.