Outlook Desktop App freezing multiple times a day – tried everything, nothing works. Help?

Posted by Bubbly-Conference745@reddit | sysadmin | View on Reddit | 75 comments

Hi guys,

our CEO's Outlook App keeps crashing and I don't know what to do more..
This is the situation: he has a Surface, and uses Teams as well as Outlook as desktop app. Teams doesn't crash. His Outlook crashes in office WIFI, as well as when he is at home. He wants to use Outlook as the desktop app and didn't want to use the desktop version as alternative.

The app is freezing multiple times a day for about 2 weeks now. The only way to close it is via Task Manager. No new emails load when it happens. Restarting the PC doesn't help.

Here's everything I've tried so far:

Safe Mode (outlook.exe /safe) – same issue, so no Add-In problem
Deleted and rebuilt the .ost file – didn't help
Online Repair via Settings → Apps → Outlook → Advanced options → Repair – no change
Checked Windows & Office Updates – all uptodate
Fully uninstalled Office with Microsoft's SaRA tool and reinstalled fresh – still freezing
Checked disk usage in Task Manager – nothing critical
Checked free space on C: – enough available
Checked RAM usage – looks fine
Checked Event Viewer – looks fine
Antivirus exclusion for Outlook – tested, no improvement
Checked Exchange connection – appears stable

System is running Microsoft 365 on Windows. Anyone have any ideas what else could cause this? Could it be hardware related?

Thanks in advance!

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Pumas32@reddit

Revert to a previous Microsoft update?

Or rename oneauth and identitycache to folders with .old and try reopening it?

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EinKompetenterMensch@reddit

Thinkbook? I have the same issue but with the new teams

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Large-Fig5187@reddit

I have used this setup with good results:

https://community.spiceworks.com/t/gmail-imap-with-outlook-2016-2019-very-slow-synching-subscribed-folders/718154

It limits which folders to sync constantly

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001droj@reddit

How big is his ost? CEO normally means they’ve never deleted a single email

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Bubbly-Conference745@reddit (OP)

good point. 18 actually..

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ShoulderRoutine6964@reddit

If it's 18 GB, that's not a problem. Outlook starts acting up after 40 GB OST/PST.

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Sammeeeeeee@reddit

I've seen 80GB work fine

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chipredacted@reddit

Are you talking about multiple mailboxes? Or PST files? Pretty much any time I've seen a mailbox OST go over 48GB, it causes problems

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Sammeeeeeee@reddit

The hard limit is 50GB but can be extended through registry

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joshtaco@reddit

Sounds like he has a retention policy in place and it needs to be cleaned out with PS

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RemarkablePin6746@reddit

Not sure if anyone has mentioned it but an April patch did the same to my outlook. Uninstalling KB5083769 fixes it. I think Microsoft have released a patch this month that fixes it but I’ve not seen it yet

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tropicalbull80@reddit

Is it in Cached Exchange Mode? We’ve experienced this behavior while trying to use Online Mode with Classic Outlook.

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caliber88@reddit

Is the surface running Snapdragon? My Thinkpad on snapdragon has been strange with classic Outlook where it would freeze sometimes when a new email comes in.

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Bubbly-Conference745@reddit (OP)

noo it doesn't but tysm for the input!

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iamMRmiagi@reddit

i7 on the replacement device? current gen is u7 is it not?

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ReasonableAnimal6182@reddit

A little late, and maybe unrelated, but there was a service health notification from Microsoft last week that showed when the Microsoft Teams Meeting Add-in for Outlook is enabled it can cause Outlook to Crash or not open.

Specifically it calls out version 26043.2016.4478.2773.

Message ID: EX1254044

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jetlagged-bee@reddit

Are you using Greenshot per chance?

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Scientist_ShadySide@reddit

Which Outlook desktop app? There is Classic and New, both with their own hnique issues.

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The_Young_Busac@reddit

This is a shot in the dark, but the symptoms you describe are similar to ones I experienced with an issue rooted in Dell peripheral manager and the port replicator being used.

Dell Peripheral Manager was trying to optimize internet connectivity by switching between WiFi and Ethernet on the device, and while the change in connection type wasn’t noticeable on web browsers, outlook would get stuck looking for the old network connection after the software made the change.

I just uninstalled peripheral manager and the issue never came back.

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mrbiggbrain@reddit

How many shared mailboxes do they have? My experience is that 2 Is about the max and after that outlook begins experiencing poor performance.

I began setting up shared mailboxes to not map automatically and had them use outlook web for less critical shared mailboxes they just want to review on occasion.

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Bubbly-Conference745@reddit (OP)

he does have 5.. i will check on this also. thank you so much for your comment!

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afristralian@reddit

Setup each mailbox as a distinct OST. (Mail icon in control panel allows you to add each mailbox as an account). Don't like it all into one OST file.

Don't know if the search indexer is still around in windows. Turn it off in windows services, turn it back on at end of day and let machine run overnight. I've seen it kill some machines performance.

(This may not help at all... It's been a while since I've touched Outlook) .

Bad hard drive is another option to consider.

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tjn182@reddit

Is there a pst file connected via network path? Always been main culprit for me

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snookajab@reddit

There’s an outlook cache folder that stores preview attachments and such. If that gets large I’ve seen it cause a slew of problems. I just don’t remember how to find it. I’m sure a google search will point you in the right direction.

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Surfin_Cow@reddit

Isn’t there a known issue with teams add-in and outlook crashing?

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RM3dIT@reddit

it might have been said already, but is the mailbox linking to shared drive, or any links to saved folders in the cloud or on prem?. i tried to link an archive .pst that id saved on a shared drive, to a users outlook. Outlook hated that idea :D (symptons was constant freezing for the 2 days i tried it with the user)

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Pleasant-Seat9884@reddit

Does he have a lot of items in his Inbox? Probably need to move them to subfolders.

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Sammeeeeeee@reddit

Delete the outlook profile and remake.

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techdispatcher@reddit

Few things that should fix it: 1) Reduce mail download window to 1-3 months for very high volume mailboxes 2) Remove some auto mapped shared mailboxes that are not critical. Check their size in exchange admin center to see their impact) or turn on online mode. 3) Educate that for high volume and multiple mailboxes there are no workarounds to keep outlook classic working well beyond a certain point. The only options are removing mail from the cache by storing a shorter window, online mode, or removing data (deleting items, removing mailboxes). Usually the causes are high mail flow to the primary mailbox or multiple shared mailboxes auto mapping like your case, or a combination of both.

To enable online mode for shared mailboxes in Outlook and ensure real-time synchronization, you must disable the "Download shared folders" setting in your account configuration.

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hybrid0404@reddit

One of the big thing I've seen as well is the number of items in the inbox. If there's >10k items just sitting in the inbox that can also be an issue, simply moving the items elsewhere can have a large impact.

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Massive_Echo7830@reddit

Is the surface intel or snapdragon ? I used to see similar issue on snapdragon processors

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Moontoya@reddit

It's a surface, that's the problem in itself

;)

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4wheels6pack@reddit

As a fellow adventurer who deals with the mysterious realm of CEOs and Outlook performance. Here’s what I’ve found.

You CAN successfully have more than 2 connected mailboxes, some people here have between 4-7 (I know, don’t ask) But in these scenarios, it’s best to use outlook in Online mode (no caching). This makes emails display slightly slower, but it prevents a lot of the .ost weirdness and shenanigans. As long as you have decent internet most people won’t notice

Th other thing I’m thinking about is mail and filtering rules. If he has a lot of items (most people never delete items) Outlook may be hanging trying to apply rules to thousands upon thousands of items. Check also his sent folder as even more conscientious people forgot to trim that

Good luck!

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concentus@reddit

Had a similar issue with several users at a client, ended up having to shut off the windows notification service for those users.

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Weak-Bus5585@reddit

Try using new outlook? That is the direction that Microsoft is moving to anyways. Outlook classic will eventually be obsolete so best make the switch now.

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Bubbly-Conference745@reddit (OP)

We are in fact using the new version of Outlook app..

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fp4@reddit

Outlook (New) is different and wouldn't have an OST file to rebuild.

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Monksnothome@reddit

I usually clear out %temp% and all folders with "cache" in the name field under %appdata% directory.

Also not a bad idea to uninstall office then scrub the computer clean of any remaining folders from office plus removing the registry keys. Running SFC and DISM restore health after is good idea to ensure everything is in good shape with the OS.

Run disk cleanup as admin to purge any left over files especially cache or driver packages possibly causing corruption or performance degradation. Then check for updates and after restarting do a fresh install of Office 365.

If still an issue after I would consider reinstalling Windows with full wipe. I've found it to sometimes be better to spend the 2 hours reinstalling Windows and reconfiguring their device than to spend multiple hours across a week or two troubleshooting down a rabbit hole.

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ralphthedog61@reddit

Is the mailbox in cached mode? Also make sure the shared mailboxes are in cached mode as well.

I had a similar issue, the user switched the mode to online. Kept complaining her system was slow.

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mihemihe@reddit

Check also what addons are running, although I think the safe mode starts Outlook without addons and you have tried that.

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nosferatoothz@reddit

Does he have any network attached .pst files? If so, have him move the emails to his M365 archive and detatch the .pst files. They are known to be super buggy and can cause issues with Outlook, especially the bigger they get.

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zephead98@reddit

I'm sorry but am I the only one who thinks spending this much time and effort to get email into a crappy app is completely asinine? I worked in a Mac shop and email was NEVER an issue. In an MS shop, it's ALWAYS an issue.

Can't he read it in a web browser? I just don't get people's addiciton to Outlook, it's like crack cocaine to them.

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Quirky-Fun-9901@reddit

I know it's always a longshot but I don't see DISM or SFC /scannow here and they do fix things on occasion. Probably not this but I've been surprised before.

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skeetgw2@reddit

Fighting that same battle with surfaces. Their quality has really gone down hill lately. Our surface 4s run better than our 7s do which is amazing to me but not shocking at all.

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bachi83@reddit

Please check ssd/hdd health.

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AppointmentIll9358@reddit

Backup his data and reinstall windows, could be a corrupted user profile

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firetroll91@reddit

This might sound crazy...

Are there old printers configured that are no longer reachable?

I had lots of problems with word freezing up when changing page orientation because an old decomissioned printer was default

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NightOfTheLivingHam@reddit

Hosted exchange or 365?

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Bubbly-Conference745@reddit (OP)

365

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LousyRaider@reddit

Our CEO was having the same problem. We have ThinkPads not surface devices, but we wiped and re-enrolled and re-configured his laptop and all has been good since.

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Bubbly-Conference745@reddit (OP)

ohhh thank you.. we can in fact try this as a last resort

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BOOZy1@reddit

Delete the contents of the OTele folder in \AppData\Local\Microsoft\Office\OTele

Evey once in a while my Outlook starts to slow down and that fixes it for a few months again.

This is with every form of telemetry turned off by policies.

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Bubbly-Conference745@reddit (OP)

thank youu!

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Typical-Road-6161@reddit

Other mailboxes connected? Test with just his and no others.

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teamonsite@reddit

This would be my suggestion also - many shared mailboxes can really cause problems

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Bubbly-Conference745@reddit (OP)

thanks for the inputs! i will try this out as well

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Typical-Road-6161@reddit

Especially if he’s connected to a departed users mailbox.

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tonkats@reddit

Lots of other people's overlaid calendars, too

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redphyrox@reddit

Check number of items in the folder. Once a folder (Inbox) hits 10,000 items, Outlook behaves weird (freezing then crashing).

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Bubbly-Conference745@reddit (OP)

thanks! i will check this

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the_doughboy@reddit

Is he against New Outlook. It’s going to be mandatory might as well switch early.

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bruteforcenet@reddit

Do you have any old crap like roaming profiles or profile redirection that could be underpinning it?

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dvr75@reddit

did you check the disk?

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binaryhextechdude@reddit

Does it freeze if someone else logs into the same computer?

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Bubbly-Conference745@reddit (OP)

haven't tried yet. but good catch

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FixDouble1405@reddit

Since it also freezes in Safe Mode and after a full Office reinstall, I’d stop treating this as a normal add-in/profile issue.

Next things I’d check:

Create a new Windows user profile and configure Outlook there.
Create a new Outlook profile, not just rebuild the OST.
Take a backup/export of the mailbox to a PST file before making major changes, so no important data is lost.
Disable hardware graphics acceleration if available.
Check mailbox size, shared mailboxes, calendars, and cached mode settings.
Test with Cached Exchange Mode off briefly.
Check whether it happens on another device with the same mailbox.

If the same mailbox freezes on another PC, suspect mailbox/calendar corruption or huge folders. If only this Surface has the issue, suspect Windows profile, graphics driver, firmware, or Surface hardware/OS corruption.

For a CEO device, I’d honestly test the mailbox on a clean spare laptop. That will tell you faster whether this is mailbox-side or machine-side.

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Bubbly-Conference745@reddit (OP)

Thank you!!!!

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bjc1960@reddit

I suppose "Outlook Web App" is out of the question.

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MagikarpHasNoNose@reddit

This will be because either the Ost file is too large and/or the app is trying to cache too many emails. Create a new profile and before it loads all the emails, go into account settings, click his email and click change, then reduce the emails to keep on device to probably half of what it is currently. Usually 6 months is fine, but you might have to change it to 3 months. If he wants to access his old emails, he can use web version.

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