NoSpamToday! for Servers - Mail Flooding Protection

Concurrent Connection Limiting

You can impose an absolute limit of concurrent connections on a port. This limit may never be reached, depending on system memory size and the memory usage limit you configured in the NoSpamToday!’s memory settings.

Mail Flooding Protection

NoSpamToday!’s traffic limiting options are also useful to protect yourself against the impact of mail flooding.

The most common kind of mail flooding are excessive amounts of non-delivery reports. This happens after a spammer or a virus is using one of your email addresses as ’From’-address and you get thousands of non-delivery reports from all around the world. Typically, you will find a pattern: only a few badly configured mail hosts are the source of these mails.

Mail servers try to deliver mail as fast as possible, and so they open more than one connection to your mail server. If a server has thousands of non-delivery reports queued for you, it can easily happen that this server alone is capable of pushing your server to its limit with spam filtering and anti virus checking for several hours. During this time, your legitimate incoming mail traffic can be slowed down to a trickle.

Sometimes it might help to send the admin of these sites a mail to inform them of the errors of their ways (they could have rejected the mail outright, instead of accepting it and sending a non-delivery report to the wrong person afterwards), but this is rarely successful.

NoSpamToday! provides the means to reduce the impact of this problem. You can put the offending mail host on a reject list, or you can limit the number of simultaneous connections accepted from the same host. This traffic limiting can be done either by host IP address (the IP address of the MTA that connects to NoSpamToday!), or by the name the MTA supplies with the SMTP HELO/EHLO command.

Learn More ...

• Read more about NoSpamToday!'s Open Relay Protection.
• Read more about NoSpamToday!'s Core Features and Benefits.