Script that checks if your mail server is in a DNSBL (DNS Blackhole List).
From heise Netze added with little features thats come from the comments.
Download it to the current directory:
curl -L -o ./dnsbl.sh https://github.com/m-hennecke/dnsbl-check/raw/master/dnsbl-check-standalone.sh
chmod 755 dnsbl.sh
The script echos found blacklist entries to stdout.
Add it to your crontab to get daily notifications:
@daily ${PATH_TO_SCRIPT}/dnsbl.sh -H YOUR_IP