Follow Techotopia on Twitter

On-line Guides
All Guides
eBook Store
iOS / Android
Linux for Beginners
Office Productivity
Linux Installation
Linux Security
Linux Utilities
Linux Virtualization
Linux Kernel
System/Network Admin
Scripting Languages
Development Tools
Web Development
GUI Toolkits/Desktop
Mail Systems
Eclipse Documentation

How To Guides
General System Admin
Linux Security
Linux Filesystems
Web Servers
Graphics & Desktop
PC Hardware
Problem Solutions
Privacy Policy




Postfix Documentation
Previous Page Home Next Page

Simple content filter limitations

The problem with content filters like the one above is that they are not very robust. The reason is that the software does not talk a well-defined protocol with Postfix. If the filter shell script aborts because the shell runs into some memory allocation problem, the script will not produce a nice exit status as defined in the file /usr/include/sysexits.h. Instead of going to the deferred queue, mail will bounce. The same lack of robustness can happen when the content filtering software itself runs into a resource problem.

The simple content filter method is not suitable for content filter actions that are invoked via header_checks or body_checks patterns. These patterns will be applied again after mail is re-injected with the Postfix sendmail command, resulting in a mail filtering loop. The advanced content filtering method (see below) makes it possible to turn off header_checks or body_checks patterns for filtered mail.

Postfix Documentation
Previous Page Home Next Page