Yes, all uribls were showing 'Attention Needed' and this brought the spool to a halt as the spam checks were so slow that there was a huge backlog - I had to suspend all the URIBLs and I just tried to reinstate but it's still happening.
Some problem with URIBL, I guess.
However, there should be some mechanism to move on of response is too slow and ignore a spam filter otherwise the problems we had this morning will recur. Maybe a 'timeout' period is required for each lookup filter,