Recovery Point Threshold Exceeded

Hi.  We've just received the message, "Used disk space for recovery point 
volume exceeds threshold of 90%".  The message lists the mail server as the

computer.

When we click the link in the message and go to the disk allocation screen, 
we find:

First Storage Group Data Size: 99Gb
Replica Volume: 200Gb
Recovery Point: 500Gb

None of these parameters suggest anything near a 90% threshold.  Any ideas?

Thanks in advance!