is there a way that i can trace what is causing the issue, i had some user say he tried to send a very large attachment and thinks it may be related? any help would be appreciated as they are currently approaching the 18GB limit on the sbs 2003 sp2. thanks.
You could use Exmon to trace usage on the mailboxes. Additionally, there's some troubleshooting steps here from users experiencing a similar problem. You can look at ESM at the user with the large attachment and see if his mailbox size is growing at all in relation to the EDB.
If you're starting to get close to the EDB limit in Exchange, you are going to want to look at putting in user restrictions on mailbox sizes and inbound/outbound attachment size limits.
If you have Exchange 2003 SP2 installed, you can increase the database size to 75 GB as outlined here. Also, Exchange only calculates the logical database size and not the physical. If you have whitespace in the EDB, then that is not counted against you.