anchor.diff:  # Private email gateway with getmail and dovecot
   #
  -# Author: gw0 [http://gw.tnode.com/] <gw.2016@tnode.com>
  +# Author: gw0 [http://gw.tnode.com/] <gw.2021@ena.one>
   
  -FROM debian:stretch
  -MAINTAINER gw0 [http://gw.tnode.com/] <gw.2016@tnode.com>
  +FROM debian:buster
  +MAINTAINER gw0 [http://gw.tnode.com/] <gw.2021@ena.one>
   
   # install debian packages
   ENV DEBIAN_FRONTEND noninteractive
   RUN apt-get update -qq \
    && apt-get install --no-install-recommends -y \
       cron \
  -    getmail4 \
  +    getmail \
       dovecot-imapd \
       dovecot-managesieved \
    && apt-get clean \
  
positive.code: # configure dovecot
  RUN sed -i 's/#log_path = syslog/log_path = \/var\/log\/dovecot\/dovecot.log/' /etc/dovecot/conf.d/10-logging.conf \
      # authentication
   && sed -i 's/#auth_verbose =.*/auth_verbose = yes/' /etc/dovecot/conf.d/10-auth.conf \
      # ssl
   && sed -i 's/^ssl =.*/ssl = required/' /etc/dovecot/conf.d/10-ssl.conf \
   && sed -i 's/#ssl_cert =.*/ssl_cert = <\/etc\/ssl\/private\/dovecot.crt/' /etc/dovecot/conf.d/10-ssl.conf \
  
negative.code:  && sed -i 's/#protocols = \$protocols sieve/protocols = \$protocols sieve/g' /etc/dovecot/conf.d/20-managesieve.conf \
      # imap idle
   && sed -i 's/#imap_idle_notify_interval =.*/imap_idle_notify_interval = 29 mins/' /etc/dovecot/conf.d/20-imap.conf \
      # fix getmail imap issue with large emails
   && sed -i 's/^_MAXLINE =.*/_MAXLINE = 10000000/' /usr/lib/python2.7/imaplib.py
  
  # setup entrypoint
  