Should filters be on left or right?
4. Filter bars better showcase filters. By making the filters more prominent on the page and by making them available as the user scrolls a filter bar does a better job of showcasing filters. Presenting filters left to right also makes it very easy for users to quickly see what options are available.
Why would you use a custom filter?
Custom filters allow you to define matching logic that cannot be accomplished using the system-provided message filters. For example, you might create a custom filter that hashes a particular message element and then examines the value to determine whether the filter should return true or false.