# ====================
# Forward E-Mails to 'do-not-reply@..' address to (file) /dev/null
# ====================

# ---
# Example for this readme:
#
# Create a forwarding to /dev/null for the address no-reply@cloud-01.oopen.de
# ---

DOMAIN=""cloud-01.oopen.de
E_MAIL="no-reply@cloud-01.oopen.de"

# see also:
#     https://www.postfix.org/VIRTUAL_README.html
#
#     https://think.unblog.ch/weiterleiten-von-postfix-alias-an-dev-null/
#     https://think.unblog.ch/en/forward-postfix-alias-to-dev-null/
#
#     https://www.serverwatch.com/guides/forwarding-a-postfix-virtual-alias-to-dev-null/


# Notice:
#     the usual solution is to forward to (file) /dev/null. In a local-only setup you could do 
#     that in /etc/aliases.
#
#     However, if your're using Postfix virtual domains, it gets a little more complicated. With 
#     virtual domains/users, you can't forward mail to a file (like /dev/null). 


# ---
# 1. Set up an alias user 'do-not-reply'that forwards incoming e-mails to /dev/null.
# ---

# Add to file '/etc/aliases' a line like:
#     do-not-reply: /dev/null

if ! $(grep -q -E "^\s*do-not-reply:" /etc/aliases 2>/devnull) ; then
   cat <<EOF >> /etc/aliases

do-not-reply: /dev/null
EOF
fi

# Renew alias database:
#
newaliases


# ---
# 2. Set up the domain (domain part of not-reply address)
# ---

# Create file '/etc/postfix/virtual_alias_domains' and add your domain '@cloud-01.oopen.de'
#
#  ${DOMAIN}         OK
#
if [[ ! -f "/etc/postfix/virtual_alias_domains" ]] ; then

   cat <<EOF >> /etc/postfix/virtual_alias_domains
# - File: /etc/postfix/virtual_alias_domains
# -
# - Note:
# -  a mapping file always has two columns. In such a 'one-dimensional' mapping (list of domains) 
# -  Postfix does not care about your second column. It does not even have to be 'OK', it can be
# -  anything.
# -
# - Example:
# -      <domain>            OK

${DOMAIN}    OK
EOF
else
   if ! $(grep -q -E "^\s*${DOMAIN}" /etc/postfix/virtual_alias_domains 2> /dev/null) ; then
      cat <<EOF >> /etc/postfix/virtual_alias_domains

${DOMAIN}    OK
EOF
   fi
fi


# Create Postfix lookup table (database file) from '/etc/postfix/virtual_alias_domains'
#
postmap btree:/etc/postfix/virtual_alias_domains


# Add virtual_alias_domains to Postfix main Configuration
#
#  ...
#  virtual_alias_domains =
#     btree:/etc/postfix/virtual_alias_domains
#  ...
#
if ! $(grep -q -E "^\s*virtual_alias_domains\s*=\s*btree:/etc/postfix/virtual_alias_domains" /etc/postfix/main.cf) \
      && ! $(grep -q -E "^\s*btree:/etc/postfix/virtual_alias_domains" /etc/postfix/main.cf); then
   perl -i -n -p -e "s#^(\s*virtual_alias_domains\s*=.*)#\1\n   btree:/etc/postfix/virtual_alias_domains#" /etc/postfix/main.cf
fi



# ---
# 3. Set up adress mapping
# ---

# - Create file '/etc/postfix/virtual_alias_maps' and add your address mapping
# -
# -      ${E_MAIL}         do-not-reply
# -
if [[ ! -f "/etc/postfix/virtual_alias_maps" ]] ; then

   cat <<EOF >> /etc/postfix/virtual_alias_maps
# - File: /etc/postfix/virtual_alias_maps
# -
# - Redirect mail for one address to one or more addresses.
# -
# - Example:
# -   # incomming address 'no-reply@cloud-01.oopen.de' to local 'do-not-reply' address
# -   no-reply@cloud-01.oopen.de    do-not-reply
# -

${E_MAIL}      do-not-reply
EOF
else
   if ! $(grep -q -E "^\s*${E_MAIL}" /etc/postfix/virtual_alias_maps 2> /dev/null) ; then
      cat <<EOF >> /etc/postfix/virtual_alias_maps

${E_MAIL}      do-not-reply
EOF
   fi
fi


# Create Postfix lookup table (database file) from '/etc/postfix/virtual_alias_maps'
#
postmap btree:/etc/postfix/virtual_alias_maps




# Add virtual_alias_maps to Postfix main Configuration
#
#  ...
#  virtual_alias_maps =
#     btree:/etc/postfix/virtual_alias_maps
#  ...
#
if ! $(grep -q -E "^\s*virtual_alias_maps\s*=\s*btree:/etc/postfix/virtual_alias_maps" /etc/postfix/main.cf) \
      && ! $(grep -q -E "^\s*btree:/etc/postfix/virtual_alias_maps" /etc/postfix/main.cf); then
   perl -i -n -p -e "s#^(\s*virtual_alias_maps\s*=.*)#\1\n   btree:/etc/postfix/virtual_alias_maps#" /etc/postfix/main.cf
fi


# ---
# 4. Reload Postfix
# ---

systemctl reload postfix