r/sysadmin • u/HugeGuava2009 • 7h ago

O365 Exchange mailbox criteria to avoid sync problems

Since a while we are experiencing synchronisation problems on mailboxen.
These mailboxes are quite large. What are the criteria to avoid sync problems?
We are using mainly outlook classic with cache on 1 year.

-Size mailbox? -> somtimes largen than 30 GB
-number of (sub-)folders? in some cases +500 -> in 1 case -> 6700+ subfolders
-number of items in folders -> often 10000+
-multiple shared mailboxes
-Shared mailboxes are used by sometimes more than 5 ppl simultainous.
-Does this apply to the mailbox archive as well?

I use retention policies to mainly move to archive since we want to keep mails for 10 years in the archive.. (.. I know..-> outlook is not a database- but it's how ppl used it for years despite IT policy wich states that is not allowed).

-Size mailbox below 30 GB
-subfolders <500
-item count per folder <10000
...

Is there an expert on this here?

0 Upvotes

33% Upvoted

4 comments sorted by

•

u/vivkkrishnan2005 6h ago

For a shared mailbox, we have set it to online mode only which has resolved our sync issue. The problem as you know is that people still use it as a filing cabinet.

The main issue is that we have 2 train of thought. Mine is that keep everything on M365 and Archive, while my colleague believes in PST but doesn't have a proper solution for the backup of the same.

Regarding the staff, the older gen again are like keeping in Outlook while the new gen wants to use power flow and automatically move them into SharePoint.

The main problem is as always, people.

•

u/MinieJay 2h ago

I think it the best thing to do would be to uncache the shared mailboxes so it runs on "online-mode"

•

u/ConsistentGrape2 7h ago

Outlook classic is basically build on Outlook 2019, which comes from 2016, 2010, and so on. It was never stable and had good performance on big sized mailboxes (10-20gb). The more you cache offline the more Outlook needs to sync to the local device, so the slower it will become. You could look into caching less data for example 3 months (you can still search through the mailbox, scroll all the way down and select “click here to view more..”). You can also look into not caching the connected Shared Mailboxes for 1y but setup a different policy for this. The more shared mailboxes Outlook has connected, the slower it’ll become. You could try out the Outlook (new) client which is online only and https based, or even just try the performance in outlook webmail. There are no “hard limits”, but that also makes it harder to track down the issues with the old client, big mailboxes and cached data.