Forum Discussion
Exchange Online Shared Mailboxes deleted after deleting disabled users from local AD
Here is the support article from Microsoft outlining what you were trying to do (with the warning not to delete the user) as well as the steps to recover if you did delete the user - https://support.office.com/en-us/article/Convert-a-user-mailbox-to-a-shared-mailbox-2e122487-e1f5-4f26-ba41-5689249d93ba
I'm also not aware of it being a license violation based on everything I've seen on the topic. I know all the users that access the shared mailbox must have a license, but not aware of any violations of using a shared mailbox to preserve a mailbox, especially if you need to continue receiving email to said mailbox. Here is another good article on the topic as well https://practical365.com/exchange-online/shared-mailboxes-vs-inactive-mailboxes-departed-users/. Still doing some looking into the licensing issue, so I'll update the thread as well if I can find any more details around it.
"Your shared mailbox can store up to 50GB of data without you assigning a license to it. After that, you need to assign a license to the mailbox to store more data."
Source: https://support.office.com/en-us/article/Create-a-shared-mailbox-871a246d-3acd-4bba-948e-5de8be0544c9
I also remember that I have a couple of shared mailboxes from 2015 and 2016 where I did exactly this: Convert to shared mailbox and delete the user account.
Inactive mailboxes are not an option for as as our employees still need access to their mailboxes and folder structure. And frankly, I don't see why I should pay for something like that.
Are you talking about a user synced from on premises AD with AD connect with the mailbox in Exchange online that was disabled, then you converted to shared mailbox and deleted the on premises object?
That would result in the mailbox being moved to deleted mailboxes because the object is gone. In a hybrid scenario you still need the object to sync to keep the mailbox active.