please use a real name when posting. Thanks.
> Is there a way to use a filter on every user in a vpopmail-domain directory
> without putting the filter in every .qmail-user file ?
Not on a per-domain basis. You can use server-wide scanners like
qmail-scanner (http://qmail-scanner.sf.net/) to do so.
> Or maybe set vpopmail
> in a way so than it includes the filter when creating a domain or user.
Would require a patch. I'm not aware of a patch that does what you want.
Feel free to create one. :)