anchor.diff:      xz-utils \
       zoo \
       && \
  -  apt-get -t stretch-backports -y install --no-install-recommends \
  +  curl https://repo.dovecot.org/DOVECOT-REPO-GPG | gpg --import && \
  +  gpg --export ED409DA1 > /etc/apt/trusted.gpg.d/dovecot.gpg && \
  +  echo "deb https://repo.dovecot.org/ce-2.3-latest/debian/stretch stretch main" > /etc/apt/sources.list.d/dovecot.list && \
  +  apt-get update -q --fix-missing && \
  +  apt-get -y install --no-install-recommends \
       dovecot-core \
       dovecot-imapd \
       dovecot-ldap \
  
positive.code:   # 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 \
      arj \
      binutils \
      bzip2 \
  
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/* && \
  