This quick guide will show you how you can create a catchall e-mail for any or all of your secondary/non-primary Google Apps domains.
So by default you can create a catchall account for the primary domain but the same option is not given for secondary/additional domains.
Luckily there is an easy work around for this and we can create a catchall address for any of your Google Apps domains.
The reason I write this post is because most of the guides I found online (when I was searching for a solution for myself) did not seem to implement this in an efficient way (applying the policy to the entire Google Apps ‘company’ rather than on individual domain basis).