Exchange Online provides the following rich features that can help your end users easily collaborate in email:

  • Site mailboxes
  • Public folders
  • Shared mailboxes
  • Groups (also called distribution groups)

Each of these features has a different user experience and feature set and should be used based on what the user needs to accomplish and what your organization can provide.

For example, site mailboxes provide great documentation collaboration features. However, site mailboxes rely on SharePoint, so if you aren’t planning on subscribing to SharePoint, you can use public folders to share documents.

So what is the difference between site mailboxes, public folders, shared mailboxes, and distribution groups?

Site mailboxes

  • For groups of people that are working together on a shared set of deliverables. They want to keep important emails and documents in one place.
  • The content is scoped to a particular project that a small team is working on. As such, all content in that mailbox is highly relevant to the team members.
  • User will not see a site mailbox in their Outlook client unless they are an owner or member of that site mailbox.
  • See this technet article for more

Public folders

  • Public folders hold the full body of shared email knowledge in an organization.
  • Public folders are a great technology for distribution group (DG) archiving. A public folder can be mail enabled and added to the DG. Emails that are sent to the DG will be automatically added to the public folder for later reference.
  • With the new Office public folders are now also available in Office 365.
  • You are limited to 50 public folder mailboxes with a maximum size of 1.25 TB. See the Exchange Online Service Description for more

Shared mailboxes

  • A group of people is working on behalf of a virtual entity (e.g. help@contoso.com). They are triaging incoming emails against a shared inbox and responding on behalf of the virtual entity.
  • Integrated document collaboration is not a requirement for this scenario.
  • Users will usually only do this for one shared mailbox and the mailbox is added manually to the user’s Outlook profile.

Distribution groups

  • Distribution groups are not actually a shared store in Exchange. They are rather a way for sending emails to a defined set of people such that emails are delivered to those users’ inboxes for triage

 

A table of comparison could look like this:

 

 

Read more here

Note

  • Public Folders not available for the Office 365 Enterprise K1, and Government K1 plans - link