Options to recover emails/mailbox if rebuild using Database Utility is not successful

The other day my Outlook on my Mac crashed after informing that a rebuild needs to be performed. After reopening Outlook, I was prompted to reenter the email server information for both my mailboxes. After closing Outlook, I proceeded to run the Database Utility and preformed the rebuild process. It completed steps 1 through 4 and the began performing step 1 again. (i presume since I have two mailboxes: one is an Exchange mailbox while the other is a POP account). After reaching step 3 of 4. the Utility crashed. On observing the hard disk space after the crash I noticed that I had 0 space remaining. Before performing the rebuild process I had about 20+ Gb of space. The mailbox identity indicated that it was about 13 Gb. I assume that the Utility crashed due to lack of space. I am in the process of freeing up a lot more space and will then perform the rebuild again. My concern is that if after performing the rebuild again that the process would not be successful in removing my data. I would appreciate if anyone can help/guide me with any options or procedure that I can follow in the event that this rebuild is not successful.

Thanks!