gnubiff 2.2.17-2build1 (amd64 binary) in ubuntu focal

 gnubiff checks for mail within a file, a qmail or MH style dir,
 or an IMAP4 or POP3 or APOP server. It can display headers (number,
 sender, subject, and date) when new mail has arrived.
 .
 While gnubiff is implemented as a GNOME panel applet, it also runs as an
 independent icon on the desktop in other environments.