Exchange 2016 - Mailbox type explanation

When provisioning mailboxes in Exchange+, it is often confusing to know what types are available and when to use each.  In summary, there are five types of mail accounts that can be created.

  • Mailbox (User mailbox)
  • Group (non-billable)
  • Resource (non-billable)
  • Contacts (non-billable)
  • Shared (non-billable)

What are they and when do I use them? 

Mailbox - This is your typical user mailbox.  Each living person in an organization that deals with email, will have a mailbox.  You can also have aliases tied to this physical mailbox, i.e.,,  You select which address is the primary/default but mail sent to any of these addresses will deliver to the same physical mailbox.

Group (AKA Distribution Groups) - Typically used for internal use, i.e.  When an email is sent to, each pre-defined person receives an email to their own individual mailbox.  If replied to, the reply will come from the individual user and the reply will go to all members of the group as well. Other typical use case might include hr@, payroll@.

Resource (AKA Equipment or Room mailbox) - Typically used for reserving and coordinating rooms and equipment.  Example: or  By copying a resource address in a meeting request, you are reserving that resource for that defined time period.  When creating your calendar event, you can confirm the resource availability.

Contacts (AKA Mail Contacts) - This is typically information about people or organizations that exist outside your Exchange organization.  Contacts can be displayed in your organizations shared address book and other address lists.

Shared (AKA Shared Mailboxes) - This type of mailbox is typically overlooked when creating an address such as sales@.  What most organizations will do is set up sales as a distribution list and forward to all members.  If you have a sales group of 25, you are forwarding and hosting 25 individual email.  When replied to, it then comes from the individual user (not sales@).  In response to this, you might bite the bullet and set up a Mailbox.  At this point, all 25 group members would need to set up this account in Outlook.  While this is a viable option, there is a better way.  A shared mailbox can be set up for sales@ and you can include all the members to this group. The user experience will be similar, in that a Windows Outlook user would see this address in their navigation pane.  At this point, all group members have access to this mailbox and correspondence can be sent from sales@ (just like a physical mailbox).

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