Exchange On Prem - User's Outlook randomly won't update/disconnects due to full access mailboxes

I knew I forgot something..We've tested with o365 Outlook & Outlook 2016.

Exchange server 2016 Version 15.2 (Build 659.4)

Not quite sure I can convince her to use webmail indefinitely. The way it is now she would have to have 10 different tabs open for all of her mailboxes.

I don't think we'll go with the MAPI adjustment either since like you said it could exhaust the server. What's curious is that we have admin accounts with full access on hundreds of mailboxes and they open up just fine with automap set to false, yet this one seems to not matter. I had thought that would be an easy fix but it has no effect on Outlook.

We'll take a look at the logs though to see if we can figure out at what point it's dying. Is it possible a specific mailbox is doing it? I think most of them are fair sized. We've moved her down to 6 total to get Outlook working again, still isn't though.

Thank you!

It could a specific one, yes. absolutely.
Is there any commonality here? Same database, etc...

and it could be her mailbox that's the issue as well :)

Or add-ins specific to her install, etc...

Do you have the luxury of isolating her mailbox and the ones she opens to their own server? ( I know, crazy)

Yea they should all be on the same database, aside from that I'm not sure about any other common thread. The issue remains regardless of computer/network so I don't think it's a local thing.

I'm leaning towards it being a mailbox issue for one of these..but curiously every time we removed a specific mailbox before it seemed to resolve, which is why I initially thought it was a max mailbox limit (or I had found the problem mailbox). However now removing that mailbox seems to have no effect.

I don't think there's any way we can isolate her to her own server, I was hoping there may be some way to narrow down if a specific mailbox is the problem but I haven't found anything that can do that yet.

Another possibility I was thinking was that it may be the mailboxes have too much mail to load up or retrieve? They are not all small mailboxes, most seem to have a hefty amount of mail.

and you could be running into this, so this may not be something easily solved unless you reduce some folders or raise that session limit I mentioned earlier

https://support.microsoft.com/en-us/help/3115602/performance-and-synchronization-problems-when-you-work-with-folders-in

Honestly, I would think about raising that session limit, at least to test and see if you encounter any issues.
From that link I had before:

https://video2.skills-academy.com/en-us/exchange/architecture/mailbox-servers/managed-store/managed-store-limits?view=exchserver-2019#:~:text=For%20more%20information%20about%20the,maximum%20session%20limits%20of%2064000

I think something has to give and if they have to work this way, then resources will need be tested, - maybe increased and get mgmt to sign off on it :)

Yup you had it, we just enacted the fix yesterday and it seems to have been successful. I've added back all of her mailboxes and they worked after we applied the fix. It ended up being the max sessions per user, we found that her session limit had been exceeded in the logs.

Got upper approval for the fix so all good for now until we move to the cloud sometime later and she ends up exceeding the mailbox limit again hah.