A shared mailbox is a type of user mailbox that doesn't have its own user name and password. As a result, users can't log into them directly. To access a shared mailbox, users must first be granted Send As or Full Access permissions to the mailbox. Once that's done, users sign into their own mailboxes and then access the shared mailbox by adding it to their Outlook profile.
To know further about SharedMailboxes and above explanation, you may get help from the links given below :
https://docs.microsoft.com/en-us/exchange/collaboration/shared-mailboxes/shared-mailboxes?view=exchserver-2019https://deakin.service-now.com/kb_view_customer.do?sys_kb_id=94aa65c44ffcaa00ffc83d501310c780 Don't forget to mark as answer my reply to your query. If this helps you ;)