[exim] Exim porc. grows very large

Hi,

I have a rather strange problem. When sending mail to a particular
domain exim processes grow to a very large size, eventually using all
available ram and slowing the server to a crawl. This does look to be
tied to sending to that one domain but I am not 100% on this.
Has anyone else seen this kind of behaviour or perhaps know why this is
happening.

Many thanks

David