[exim] hold mail for specific users

Is it possible to hold mail for a list of users for one specific domain?
I'm aware of the hold domain verb however I only want to hold specific
users mail.
Can this be done with a router/transport combination ie write to file
for re-injection or simlilar?

Thanks

Ronan
--
Regards

Ronan McGlue

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Analyst / Programmer
Queens University Belfast