anchor.diff:    # TODO installing postfix with --no-install-recommends makes "checking ssl: generated default cert works correctly" fail
     apt-get -y install --no-install-recommends \
       amavisd-new \
  +    apt-transport-https \
       arj \
       binutils \
       bzip2 \
  
positive.code:     xz-utils \
      zoo \
      && \
    apt-get -t stretch-backports -y install --no-install-recommends \
      dovecot-core \
      dovecot-imapd \
      dovecot-ldap \
  
negative.code:     dovecot-pop3d \
      dovecot-sieve \
      && \
    sed -i 's/CERTDIR=.*/CERTDIR=\/etc\/dovecot\/ssl/g' /usr/share/dovecot/mkcert.sh && \
    sed -i 's/KEYDIR=.*/KEYDIR=\/etc\/dovecot\/ssl/g' /usr/share/dovecot/mkcert.sh && \
    sed -i 's/KEYFILE=.*/KEYFILE=\$KEYDIR\/dovecot.key/g' /usr/share/dovecot/mkcert.sh && \
    apt-get autoclean && \
    rm -rf /var/lib/apt/lists/* && \
    rm -rf /usr/share/locale/* && \
  