Weird Outlook sync issues - Exchange

DeaconFrost

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Sep 6, 2007
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I was drafted in to help our helpdesk guy with a strange issue. Our CEO has a problem with Outlook not completely syncing with our server. His Outlook client on his laptop gets new e-mails as expected, but doesn't seem to be syncing his Sent Items, or any changes he makes, such as deleting items from his inbox. However, if he deletes an item on his phone, his Outlook client will get the change. If he sends a message from Outlook on his laptop, it goes through, but doesn't show up on the server or his phone under Sent Items.

As a solution, we've tried repairing Office. I've removed Office and reinstalled. We can always delete his .ost, but then he'll loose changes he's made locally. I have it backed up to .pst, just in case.

As some background, we're running Office 365, but using on-prem Exchange 2016 servers.His .ost was 97 GB in space, but I was able to compact that down to 66 GB. We have the registry keys in place to allow such a large .ost file, but he has had frequent issues. Obviously, the easiest solution is to have him archive e-mail, but I'm looking for any options or suggestions before that.
 

Kardonxt

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Apr 13, 2009
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3,155
I have never had a good experience with 50gb+ OST files. I would recommend enabling online \ in-place archiving if your 365 package supports it. Then his archive follows him across devices and you don't have to worry about managing it locally.
 

Bowman15

[H]ard|Gawd
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Apr 7, 2015
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OP try this reg hack on his pc...this has solved a lot of snyc and login issues for Office 365. We are deploying it now with a ton of gotchyas...and this has cured most. Might do nothing, or fix it. Make sure to reboot after applying.

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover]
"ExcludeExplicitO365Endpoint"=dword:00000001
 

DeaconFrost

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Looks like we have that registry key in place already. My guess is, our Exchange guru did this, knowing we are using on-prem Exchange.
 

Spartacus09

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Microsoft recommends under 2gb for proper performance. My only suggestion if you just ‘cant archive’ is try online only mode ~ you can make a second outlook profile to try it (assuming he has a hardwire connection and good internet). My last ceo was very similar we finally convinced him when he got to 30gb to archive everything by year to pst and only have the current year on ost.

Biggest issue was being, his assistant also had 3 other execs and him, and all had delegated their mailboxes for calendar and mail, the EA was pushing 60+ and could only function in online only mode (it was a litte laggy at times but functioned 1-2 load for a selected item).

IMO you need to get that file under 10gb by whatever means necessary, blow away the profile and have it redownload fresh. Otherwise a online mode plus even a desktop, then a laptop that only syncs a months worth of email.
 

DeaconFrost

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So far, that's been working much better. We set it at 2 years, and there haven't been any issues since. We're looking in to an Enterprise archiving setup, because others will have this issue, too. We, ugh, aren't allowed to limit mailbox sizes.
 

kennyluu87

Weaksauce
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Mar 4, 2020
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Look into CrashPlan for archiving. I've been using this and haven't had any issues. What's nice about crash plan is itll save historical data like shadow copy. Also, it can be ran when system and files are still active.
 

Easius

Limp Gawd
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Jan 1, 2009
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354
Regarding the OP - at 97GB ost I would look at archiving mail for sure. Reducing per-folder item count helps performance alot. Make sure he has an SSD and rebuild his profile as well.

Microsoft recommends under 2gb for proper performance.
2GB is a very old metric from back in the ANSI days. The newer versions of exchange/outlook are just fine running much larger database sizes. In my experience if you have decent iops on the client you can easily surpass 10gb.I have plenty of clients running 25GB+ OSTs without issue. The key is definitely a good computer to process the caches unicode DB. i5s/8GB+ RAM/SSD minimum.

I have one client running online mode with Exchange 2016 but it's because they have a full SSD-RAID 10 and gigabit to all workstations. Using online mode with Office 365 is less than desirable IMHO.
 

Spartacus09

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Apr 21, 2018
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Agreed, my knowledge comes from office 2013, it was 2gb ost still for that version when it first released. So its a bit dated, just trying to give suggestions of things to try to resolve the issue.
 

DeaconFrost

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We were in the process of switching from MailProtector to MimeCast which offers all of our spam-filtering needs plus archiving. So far, the mailbox has been better after limiting the amount of time Outlook kept synced locally, but the user has volunteered to be one of the first to have his mailbox archived.
 
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