Postfix support added to "IPBlock" functionality for SMTP connection throttling.

"SMTP Connection Throttling" or "Rate Limiting" functionality that limits the incoming SMTP connections on your MailServer now also supports the Postfix MTA as well. Known as "IPBlock" in MailScanner this feature limits the incoming SMTP connections on your server.

SMTP connection throttling is a major requirement for all Email Service providers in the age where Spams and Viruses rule the Internet traffic. The Spammers or Viruses bombard mails on mailservers, causing un-necessary increase in load on the servers and delay in the legitimate mail flow. As a result a feature like IPBlock becomes very necessary to put a limit. This in general terms is called as "Rate Limiting" in which you can control the number of connections originating from an IP address or a remote Zombie machine. If the number of connections coming in from a machine exceeds the alloted quota (which can be the default value or specific value for a specific address) for a given hour, then the server starts refusing further connections from the remote machine.

But the mailservers had to be dependent either on the MTA or the firewall to get this feature. However some MTAs like Postfix hasn't implemented this feature as yet and is still the CVS. Having this feature in the Firewall makes it difficult to track the blocked IPs and whitelist any one if required. Also implementation at the firewall level needs a good understanding of the Firewall concepts.

IPBlock on MailScanner is specifically meant to answer the issue and give the ease to manage the blocked IP addresses. However in the earlier version it was meant to support only Sendmail MTA. This has now been changed to support the Postfix MTA as well from MailScanner version 4.38.3 onwards released on 18th Jan 2005. The script automatically detects the MTA being used for MailScanner and sets the appropriate settings specific for the MTA.

The changelog for version (4.38.3) is available at the following link
http://www.sng.ecs.soton.ac.uk/mailscanner/ChangeLog