SOLVED

Question about Exchange Online limits in regards of Outlook connectivity

MVP

Hello all,

Just a quick question about Exchange Online limits: is there any limit in regards of how many times a EXO inbox can be configured in Outlook client? I have a customer that is having problems when an EXO inbox is configured in Outlook client more than 20 - 25 times? Does any of the Exchange Experts in the house know if this is a know limit? cc @Vasil Michev @Tony Redmond

5 Replies
There are limits, however Microsoft is not publishing those publicly (and they removed the relevant cmdlets years ago). You can get the limits for on-prem Exchange on TechNet, they can serve as educated guess. For example https://technet.microsoft.com/en-us/library/ff477612(v=exchg.141).aspx

Best i can do from mobile device, sorry :)

"When an EXO mailbox is configured in Outlook..."  What precisely do you mean when a mailbox is configured? I am unaware of any situations where a configuration change (like changing a mailbox property) would count against some limit. But do tell us exactly what this person is doing so that we can all ponder the great unknown...

Ey Tony, I mean configure Outlook to use a particular mailbox and this mailbox is configured in several PCs/Laptops. According to my customer, after configuring Outlook in 20-25 PCs/Laptops, they start seing th mailbox is not added to Outlook due to some kind of corruption of OST file
best response confirmed by Juan Carlos González Martín (MVP)
Solution

So it's a shared mailbox... and yes, once you start to ramp up the number of concurrent accesses to a shared mailbox, you start to encounter performance and other difficulties. Why would they use a shared mailbox for this purpose instead of an Office 365 Group, which will have its own synchronization (to the GST, not OST), and so avoid the issue?

Yeap, it's a shared MailBox...they are using that shared mailbox just because of delegation (SendAs)...something that can also be done with a Group, so this is a great advice and I'm going to suggest to my customer. Thanks Tony!