Thank you for using Outlook Mobile and sharing your ideas with us. We really appreciate your support.
It is currently already possible to set an out of office message in the app for Outlook.com Exchange and Office 365 accounts.
To setup out of the office replies, tap settings > tap your Office365, Outlook.com or Exchange account > tap Automatic Replies > toggle the switch on.
You may choose:
1.) Reply to everyone
2.) Reply only to my organization
You can also set up a different messages for your organization and external senders.
Tap done once you have set up your automatic reply.
Having trouble finding the feature? Let us know through the Help section of the app. You may reach them by going to the app’s Setting > Help and Feedback > Contact Support
Thank you again for your support, we look forward to hearing more of your ideas very soon.
All the best
The Outlook Mobile Team
PS: Please use the Help Section of the app for any questions, we are not able to see replies to this address.