It’s quite common for teams that use a shared mailbox as an inbound communication channel to user sub-folder to sort or file away items that have been actioned. There is some demand for Group mailboxes to have sub-folders, as shown in the comments on this Uservoice suggestion. Shared mailboxes have more granular permissions available than Groups do.Shared mailboxes can have sub-folders in the mailbox, whereas Group mailboxes can’t.However, shared mailboxes have some capabilities that may make them more suitable to teams than Groups. Groups have connectors for integrating other applications.Groups have a guest access model for external collaboration that shared mailboxes do not.Groups include additional collaboration apps and resources such as a SharePoint team site, OneNote notebook, Planner, and Teams.Users (members) can subscribe to receive a copy in their own mailbox of the emails sent to the Group mailbox, which makes Groups work in a similar manner to distribution lists.Office 365 Groups have additional features that shared mailboxes do not. Emails sent to Groups and shared mailboxes are preserved for historical reference, unless deleted by a user.Users can send-as or send-on-behalf of a Group mailbox, just as they would a shared mailbox.

A Group mailbox can be used as a single point of email contact for a team or group of users, just as a shared mailbox can be.

Multiple users can access a Group mailbox, just as they would a shared mailbox.Groups in Office 365 have many of the features that Exchange Online shared mailboxes do. I was recently asked for my thoughts on using Office 365 Groups instead of shared mailboxes. Comparing Shared Mailboxes and Office 365 Groups: the 2017 View Update (November 2022): Read Tony Redmond’s take on this topic five years on after Microsoft has given Outlook Groups a lot more functionality.

Exchange online shared mailboxes