[Exim] Ignoring re-try rules for a given server

I want to always attempt a delivery from my inbound mail server to the
server which holds my users mailboxes. The user server occasionally rejects
mail because it's busy, causing the inbound server to clog as it waits to
retry. I've tried defining a retry rule:

[10.250.1.20]    *    F,15s,5m; G,4d,1h,1,5

but this doesn't seem to work.

How can I make the inbound server ALWAYS attempt a delivery to the user
server?


Cheers

Al