[exim] Block email with dates far in the past

Hi everyone,

I'm noticing a lot of spam lately that is using a date far in the past, presumably to ensure it shows up near the top of an inbox. For example, I received two yesterday which were dated August 2.

Is there a way to filter messages and reject them if their header dates are just too far in the past? I think a threshold of a couple weeks is more than sufficient to allow for retries in the event of a delivery problem but after that any sane system would simply give up.

Thanks