Exchange 2019 Shared Mailbox limitations.

Question

Hi Guys,

I have a User Mailbox in the company which is used as a "Shared Mailbox". I would like to tidy it up and convert it to Shared Mailbox. My questions are:

1. What are the limitations regarding the maximum number of connections(in same time) to Shared Mailbox on the Exchange 2019 server?
2. After converting User Mailbox to Shared Mailbox, will the previously configured permissions (full access, send ass) remain or will they need to be re-assigned?
3. As we use a hybrid solution, we have Users in the cloud, and the new Shared Mailbox(converted from User Mailbox) will be on the on-premise server. Are there any other limitations with this configuration?

This is a very active mailbox (more than 50 users use it at the same time). How best to solve it? Migrating the object to Online is not an option.

BR,

TZ

Answer 1

Hi @Tomasz Zakrzewski ,

1. There doesn't seem to be clear documentation from Microsoft about the limit specific for shared mailbox. however, there are some store limitations in on-premises Exchange such as "session limits” and I think that can be applied to shared mailbox as well:

Check this: Managed Store Limits in Exchange 2016 and Exchange 2019 | Microsoft Learn

2.When converting a user mailbox to a shared mailbox, only the mailbox type is changed. All existing email and calendar items, mailbox and folder permissions, and mailbox rules are preserved. So, the previously assigned permissions will be preserved.

3. If you are referring to whether there is any restriction on whether cloud users can access On-premises shared mailboxes, as far as I know, there should be no restrictions.

Regards

Shaofan

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Answer 2

Even though this is listed for Exchange Online, I generally follow this same guidance for on-prem Exchange:

https://learn.microsoft.com/en-us/microsoft-365/admin/email/about-shared-mailboxes?view=o365-worldwide