[exim] 451 resulting in permanent error / retry problem

Hi guys,

I have a strange problem and need a hint in the right direction. Sorry
for obfuscation of the addresses, should do no harm though:

2007-05-29 12:42:43 1Hsz9w-0006Ni-Nn SMTP error from remote mail server
after RCPT TO:<schmidt@???>: host smtpsp1.test.de
[130.83.44.80]: 451 4.7.1 Greylisting in progress, please come back
later
2007-05-29 12:42:44 1Hsz9w-0006Ni-Nn == schmidt@???
R=dns_from_internal T=remote_smtp defer (-44): SMTP error from remote
mail server after RCPT TO:<schmidt@???>: host smtpsp2.test.de
[130.83.44.81]: 451 4.7.1 Greylisting in progress, please come back
later
2007-05-29 12:42:44 1Hsz9w-0006Ni-Nn ** schmidt@???: retry
timeout exceeded
2007-05-29 12:42:44 1HszA4-0006OZ-2I <= <> R=1Hsz9w-0006Ni-Nn U=mailnull
P=local S=4923 from <> for j.koopmann@???
2007-05-29 12:42:44 1Hsz9w-0006Ni-Nn Completed

As you can see the recipient MXs are using greylisting. So far so good.
What I do not understand is that Exim after two tries decides "retry
timeout exceeded" and sends a NDR immediatly? The working retry rule is
this:

exim -C /usr/local/etc/exim/configure.out -brt schmidt@???
Retry rule: * * F,2h,15m; G,16h,1h,1.5; F,4d,6h;

So this should try a lot longer. What am I missing?

Kind regards,
JP