What would cause soap requests to spike?

[i2ambler]

I noticed yesterday that my mail servers became slowwwww at a speicific time.. ( I have 2 ) I noticed that one of the servers - lets call it mailstore1 - was up to a 12.0 load.. It was only up there for a couple of minutes.

Today I grabbed a zmstat chart and noticed that when the load was super high (around 12) the soap calls/sec skyrocketed to 700 instead of the steady 100 or so - also at that time mailbox delivery latency went up - connection pool latency went up as well and mysql database connections went way up as well..

This is really weird! We dont have any location come online at that time, or an unusual amount of people logging in. Does anyone have any clue what may cause this?