dovecot.conf

  passdb passwd-file {
    args = /home/vmail/%d/passwd
  }

  passdb pam {
    args = session=yes dovecot
  }
  
  userdb static {
    args = uid=vmail gid=dovecot home=/home/vmail/%d/%u
  }
  
  userdb passwd {
    args = blocking=yes
  }