Lock down Outlook Web Access.
28. Disable or lock down Outlook Web Access.
Outlook Web Access, either from an on-premises server or Office 365, provides nice mobility and functionality. It also provides another doorway into your mailbox for those you may want to keep out.
Disabling Outlook Web Access closes a back door. Locking it down to associated geographical IP addresses (say, to the United States) prevents access to firm resources from abroad.