It's long frustrated me that I can set up out-of-office alerts for Exchange accounts from the Mac's Mail application but not iOS's Mail. Now I can, and so can you. Say bye-bye to that awkward Outlook Web Access browser interface on your iOS device.
You set up out-of-office notifications in the Settings app's Mail, Contacts, Calendars pane. Tap your Exchange or Office 365 account, then tap Automatic Reply to open the form shown here. It has the same options as Microsoft's OWA for iPad app: You can set an end date and a reply that everyone sees when they email you during that period.
Note: This feature is available only for Exchange accounts, not iCloud, Gmail, or IMAP.