Mutt new mail indication in gnu screen

gistfile1.txt

muttrc:

set status_format="/home/maat/run/bin/mutt_newmail '%b' '%n' '-%r-ubu: %f [Msgs:%?M?%M/?%m%?  n? New:%n?%?o? Old:%o?%?d? Del:%d?%?F? Flag:%F?%?t? Tag:%t?%?p? Post:%p?%?b? Inc:%b?%?l? %l?]---(%s/%S)-%>-(%  P)---'"|

/home/maat/run/bin/mutt_newmail:

  #!/bin/bash
  if [ "${1:-0}${2:-0}" = 00 ]
  then
          printf "\033kposta\033\\" > /dev/tty
  else
          printf "\033kPOSTA!\033\\" > /dev/tty
  fi
  
  echo "$3"