[Exim] Redirecting unknown accounts

Hello exim-users,

[Please CC: me as I am not subscribed. Thanks.]

What's the cleanest / best way to achieve the following with Exim?

Redirect mail for all non-existant accounts to a specific user. That
means that those mails shouldn't result in a 'postmaster' warning as
normally is the case; but they should be delivered to a specific account
instead.

Mails for accounts that exist should be delivered as normally.

Cheers,
Sven