Outlook app draining battery

Same serious problem. No fix. No choice but to delete Outlook.

How do you release an update so poorly executed that it actually destroys phones? And still can't fix it?

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

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...

The most recent update seems to be a battery killer. I didn't pay attention to when Outlook got updated, but overnight my battery was dying after 4 hours. I'd go to the store and it would drop to 68%. Uninstalling Outlook solved my battery drain problem.

I work at a Microsoft campus, so I prefer to use native MS tools. But I cannot keep an app on my phone with this kind of drain. I'll monitor this thread, and if it sounds like the issue gets resolved, then I'll reinstall. But I'm not a fan of testing their updates for them.

So far it's still working fine for me. I uninstalled, reinstalled & then turned off the auto updates in my Google Play Store. I manually go in & update my apps except for Outlook & battery is doing fine. So, if you do the uninstall & reinstall, do not allow it to update.