ORDBScan is a Perl software that scans sendmail logs for ORDB (Open Relay DataBase) bounces. This tool helps users detect and address any potential email delivery issues caused by ORDB bounces through its scanning capabilities.
In our experience, most ORDB rejections are spam, but occasionally we come across false positives, which are blocked mail from people with whom we want to interact. Even though these people are running insecure mail servers, the use of this tool helps us to direct them on how to fix their servers.
ordbscan is a powerful tool that processes sendmail log files and reports on all the mail bounced by ORDB. A visual scan of the output usually shows the "obvious" candidates for further investigation.
It's important to note that in order to use ordbscan effectively, a delay_checks feature needs to be added to sendmail. Without this feature, sendmail will reject mail from open relays very early in the SMTP conversation before recipients can be determined. This will result in a less efficient use of the tool.
Adding ORDB support to sendmail is straightforward. Simply add these two lines to the normal sendmail ".mc" macros file:
FEATURE(`delay_checks')dnl
FEATURE(`dnsbl', `relays.ordb.org', `Rejected - see ')dnl
Rebuild the configuration and "kick" sendmail. Mail from insecure servers will then be rejected and logged. It's important to remember that the delay_checks feature plays a crucial role in using ordbscan, and without it, the tool is of limited use.