cPanel Version 11.24.4-RELEASE, build 36167

I'm trying to add a filter to forward everything that's sent to "" (where 'foo' can be any alphanumeric sequence). To do this, I've set up an account level filter:

[To] [Begins with] [philpem.]

[Redirect to email] [<my email here>]
I also have Default Address set to ":fail No such person here"

If I send mail from the server to '', then the mail is passed along successfully.
If I attempt to send that same email from (say) Gmail to the same address, it's bounced with the error I set under Default Address (550 No such person here).
If I run a mail trace, I get one red-bordered box:
virtual_aliases via virtual_aliases router forced address failure
What is going on here? All I want is for mail with a given prefix to go through to my main email account.

I've been into WHM and re-saved the Exim config, but this hasn't made any difference. I'm tempted to force a cPanel and Exim upgrade but this seems a bit of a "sledgehammer to crack a nut" solution to the problem...

Can anyone offer any assistance with this issue?