Is there a setting within the iOS that we can set how much email is available when offline, it seems that I can never open attachments when offline and that the main Inbox folder only dates back 1 week.
its quite an important to my business as many users work offline and on flights and currently, we're seeing issues of not being able to open attachments that have already been viewed or going back further than a week of email.
@bprater I have checked all configuration options and can confirm that there is definitely NOT any offline option for iOS Outlook. The new Office Beta for iOS that came out this month also makes NO change to this.
I also checked all back-end configuration that IT admins have (including MDM profiles) and there is no such option to set "offline download/cache" like you can with ActiveSync (the old Apple Mail).
This means currently, your only option is to go back to using the Apple iOS mail app via exchange.