[Exim] Full Queue

Hi all,

I'm getting full queues,
Some of the internal e-mails are taking 20 minutes to send,
I'm using exim -bd -q15m,
is it just that the queue runners are taking their time? .. we usually have
an average delivery time of 2.4 minutes for mails which don't encounter any
problems ... this is working it's way up to 14 minutes.

any help gratefully received,

Zed