Be careful when enabling auditing on the Mailbox entity. As Jukka “Kalsarikännit” Niiranen has discovered after analyzing why one of the instance consumed disproportional storage:

“It all looked fine at first, but looks like at some point the sync process had started to update the exchangesyncstatexml field with new data every few minutes. [This] field … is hidden from the UI, and also a field for which I cannot selectively disable the audit for, since the Mailbox entity fields are not editable. Oh well, time to delete our entire CRM audit log history and move on…”

In the cases where the audit contains valuable business data, deleting the audit log history as a cleanup measure is a tricky business, especially for CRM Online.