Running Exchange Server 2003 Server. I've got a problem where one mailbox is reporting the wrong size. Looking into her mailbox she does not have a lot saved there, and nothing in her mailbox has an attachment or set of attachments that would bring the size of the mailbox to what it is. I've looked and double checked her folder list and have also downloaded an information store viewer to checkout the Top of Information Store for her account as it was suggested emails may be "lost" in that area. There was nothing. Does anyone have other suggestions about resetting her mailbox size so it shows the correct size?

You're comparing her mailbox size reported in Outlook to the size reported in ESM? What's your deleted item retention set to?

Yes I'm looking at her mailbox size in the ESM. From there I checked her Outlook box for excessive messages and large attachements. Finally I checked the top of information store. Deleted items stay in mailboxes for 7 days but we've emptied her mailbox through outlook.

If you have multiple mailbox databases, try moving her mailbox to another database. Or perhaps, if in cached mode, try deleting and re-creating the OST.