Alternatives to Exchange 365 Shared Mailboxes

We have around 250 users in multiple locations around the world.  There are also over 300 shared mailboxes that are accessed.  As more shared mailboxes are added, it has caused numerous problems with outlook load times, syncing, and overall performance because some users will have 10, 20, even 50 shared mailboxes attached depending on their access rights.  

I was shocked to find that one user had over 180 shared mailboxes attached and he was flabbergasted as to why it would take outlook a half hour to open and tended to crash and run slowly.  I've tried all sorts of variations of cached/non-cached modes and other settings to help alleviate the issues, but the problem usually just comes down to the amount of shared mailboxes they have.

I need to find a way to either improve the current setup, or switch to some other method of sharing mail that goes to these inboxes.
We have an added complication that it's a financial firm, so it has a number of policies and other things in place that the solution would need to be able to comply with.

Any suggestions?
sfcandersonAsked:
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Mahesh SharmaCommented:
You may want to disable Auto-mapping feature for mailboxes

https://support.microsoft.com/en-us/kb/2646504

This way mailboxes wouldn't auto show up in outlook and other required mailboxes may be configured in Outlook profile
Mahesh SharmaCommented:
Mahesh SharmaCommented:
Another solution may be removing the direct permissions from shared mailboxes, adding security groups for permissions and then adding required users to those security groups.
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sfcandersonAuthor Commented:
Huh.  One or the other of those solutions wouldn't be helpful, but if we did both it would have the benefit of reduced mappings without out the problem of keeping track of permissions, so that's a good start, thanks!

But, for the users that need a constant eye on their attached mailboxes and have many of them, is there any alternative that you can think of to reduce the burden it places on Outlook? A different type of mailbox, or another mail system, or additional software?
Mahesh SharmaCommented:
Outlook performance is going to be sluggish if we are using too many mailboxes within outlook profile

We may consider adding the shared mailbox as Additional mailbox rather than Additional account in Outlook profile.
https://support.microsoft.com/en-us/kb/981245
Vasil Michev (MVP)Commented:
The biggest question here is why do they have that many shared mailboxes? Are all of them really needed and can they be consolidated? I highly doubt they need access to all shared mailboxes at all times, so removing unnecessary ones and adjusting automapping is a good start. Next, you can instruct them to open only the mailboxes they need on a daily basis in Outlook, and access the rest via OWA.

Switching to Modern groups might also be an option.
sfcandersonAuthor Commented:
Vasil,  Unfortunately OWA is disabled for security policy purposes.  It's a financial firm and each of the mailboxes is a different account.

I agree with your suggestion for consolidation.

In my research I ran into an article that recommended a shared inbox could boost team productivity. We may be able to consolidate some like accounts into one shared inbox, have a security group as the only full access member, and give it aliases for each of the separate accounts.  With Mail flow rules we could have the subject line prepended with the intended alias to easily identify what belongs to what inside the shared inbox.  Could then also have online rules to filter the mail to specific subfolders if desired.

Anyone see any potential problems with that idea?
Vasil Michev (MVP)Commented:
The usual problems we have with shared mailboxes is what you have already run into - bloated profiles, slow Outlook, etc. If OWA is not an option, then perhaps you can at least convince them to use separate Outlook profiles for at least some of those shared mailboxes, so that their main profile survives a bit longer :)

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