16Gb databse limit and event viewer messages

[NortonES2]

I'm puzzled, I know that Exchange standard has a limit of 16Gb for the private information store. However one of our servers stopped delivering email yesterday because this limit was reached. What confuses me is 1 hour earlier in the event viewer there was a message stating that the private info store has 6Gb available.

I know we didn't receive over 6Gb of email in that hour so:-

Are the event viewer messages mis-leading?
Does Exchange not efficiently re-use this space?

After an off-line defrag was run the priv info store was approx 9Gb which corresponds to the 6Gb available as stated in the event viewer.

Yours
confused of IT.

-------------------------------

If it doesn't leak oil it must be empty!!

 

[NortonES2]

Below is the event viewer message showing (I believe) 6Gb available:-

The database "First Storage Group\Mailbox Store (EXCHANGE)" has 6519 megabytes of free space after online defragmentation has terminated.

and here is the message 1 hour later:-

Information Store (2084) First Storage Group: The database E:\Exchange\priv1.edb has reached its maximum size of 16383 MB. If the database cannot be restarted, an offline defragmentation may be performed to reduce its size.


-------------------------------

If it doesn't leak oil it must be empty!!