Outlook app draining battery

I deleted the app and went with the BlackBerry Hub apps. No issues. Stock apps work as well.

I made a few changes and Outlook for Android seems to be running normal again.  Note, though, that all phones will not respond favorably to the same fixes, so only some or none of my tweaks may work for you.

A few months ago my Moto Z Force (Verizon Android 7.1.1) starting sucking the battery very quickly.  Phone has 64MB resident memory and was less than 50% full; SD card was only 10% full.  Motorola senior level technician provided support and could not find anything wrong with the hardware.  One year old battery was determined to be in good condition.  

I reset the phone to factory defaults and manually reinstalled the apps.  After setting up Outlook I noticed that the Contacts button was gone.  I really didn't care, though, because the Outlook Contacts feature has always been problematic and unreliable, so I ended up having to use the phone's resident Contacts app anyway.  After a few weeks I started noticing another unusual battery drain on my phone again, but this time even worse.  A bit of troubleshooting revealed that Outlook was putting a serious drain on the battery (and probably the CPU, too).  I could even feel the phone physically overheating!  Closing the app yielded the same results, so it was clearly running full blown in the background.  I could have decided to "force close" the app every time I finish an email session, but then what's the point of having the app at all, right?  If there was a setting in the OS to disable an app from running in the background, like in Windows, then this would solve the problem, but I am not aware of any such option.  

After reading this thread I decided to give Outlook one last fresh start and then move to another e-mail app if this failed.  First, I cleared the cache and app data for Outlook, then uninstalled the app.  Rebooted the phone.  Reinstalled Outlook, and made sure to leave the Contacts sync turned off.  I also unchecked all of the Add-Ins, such as EverNote, etc.  This is probably not relevant, but my Outlook has two accounts; one MS Exchange and one Office 365.  The "screen" is accounting for many times more battery drain than all of the other apps and OS, all of which are at minim levels (including Outlook, which I am leaving open).  In case you are wondering... WhatsApp, Textra, Phone, Chrome, Google Maps, Podcast Addict and OneNote apps are all open and running.  GPS is active, WiFi is off and bluetooth is on.  Also, a weather widget is running on my home screen.  

Known Facts:

1. Uninstalling the fully updated Outlook for Android app and reinstalling it yielded an entirely new version of Office 365.  I would really like to know why this did not happen through regular updates.
2. Wiping the phone resolved a problem of Excel, Word and OneNote from failing to load.  
3. Phone did not start having battery drain problems until earlier this year.  
4. Android 8.0 Oreo is being released by Verizon in a few weeks.  I am holding my breath in hopes that I can defer the update until a minor updated to v8 is released, in order to avoid major update bugs.  I heard that Verizon is pushing OS updates now, though, and that only rooted users can avoid it.
5. Microsoft will only provide basic level tech support, and the personnel at this level have less technical acumen than I do, so this is a worthless resource.  

I will continue to monitor battery usage this week, and post something to this thread if anything changes.  If all is well then I will turn Contacts Sync on and see how it goes...

When I enabled App Permissions under security, Outlook started to prompt me in an infinite loop to allow it to access contacts and whenever I gave the permission it asked again, so it looks, that if contacts sync is enabled Outlook keeps spamming the contact list with sync. I disabled the contact sync on my outlook account and it seems that cpu usage is now lower, and also some guy from another forum said that this fixed his battery draining issue. I hope this will fix it, otherwise I'll stop using it as well. Shame on you Microsoft -.-

Stopped the contact sync in Outlook and problem resolved. Thanks for the solution.

But it says that it will delete all contacts from the phone - Did it? 

So I was having the same battery drain issues as everyone else and turning Contact Sync "OFF" immediately solved the problem. I can do that as I'm using the desktop app Contacts Sync Pro to sync all my contacts from my Windows desktop Outlook client to my Google Contacts which then makes them available on my Android phones. 

Having Sync Contacts on in the Outlook Android client was just adding duplicate versions of those contacts to my phone's contact database, so I didn't need it anyway.  Turning it off did remove those contact records that Outlook for Android added but it didn't remove any of my contacts that were synced via Contacts Sync Pro (or any other contacts I had added to my Google account Contacts). 

Besides the battery drain this was causing major performance issues on my Blackberry KeyONE which I use for my work email and use the Outlook for Android app on. Once I turned off the Contact Sync option the phone's responsiveness returned. I had tried deleting the Outlook app and reinstalling it but after about 10 minutes the performance and battery drain issues returned.

I think the Outlook Contact Sync process is doing something screwy to Google Play Services, it's battery usage was extreme in tandem with Outlook's, and was forcing Google Play Services to be running 100% CPU time (meaning when you look at it's CPU Total time in app usage details, it's CPU time was exactly equal to the amount of time the phone had been on battery/not charging - that's crazy when you consider the Android System app only has used a quarter of that CPU time).

Come on Microsoft - Do something about this.  You are losing customers fast..................

Google Play store shows a update for Outlook app, with date of May 10th, but no Version number.  I tried to push app from the store to my test phone but it keeps downloading 2.2.151, which is update from May 4th causing issues.

Come on Microsoft...couple more days and you are going to lose my business going forward for all Android devices.