[Exim] remove old frozen messages

Hello,

I've a stupid question but I can't find the answer...

I've 1156 frozen messages from the 15th of October 1999 (it's the day I
began to run Exim).

My question is : How can I delete them without deleting non-frozen
messages.

PS: I run exim with the standard options: -bd -q30m

Thanks.