Was having similar issues was described by several:
Mobile Device: Samsung Galaxy 25
Behaviors experienced:
- Outlookobile defaulted all system folders (inbox, sent items, drafts, meetings, all menu items) was in another language (Spanish in my case).
- setting the Outlook language to English would fix it until I moved to inbox or any other folder or went back into settings
- setting the Outlook language to "system default" (which is English for me) would do the same as above.
- Clearing cache, uninstalling the app, etc did not work
Solution:
In Android System Settings , navigate to General Management, go to Language and delete the additional languages (in my case, left English as the only one).
Then under General Management l, go to Language Packs and do the same (I'm pretty sure this was unnecessarybuy I did both of these things and it worked for me whereas nothing else worked for days)...
I'll be installing the secondary language again since it helps detect Spanish (or w/e other languages you use) words in auto correct and the swipe keyboard.
Hope this helps others