Office 365

Office 365 exchange mailbox types

The five types of mail accounts that you can create are:

Mailbox (Requires License)
Group (Free)
Resource (Free)
Contacts (Free)
Shared (Free)
I will first describe each type and when you should use it, and later get into some details.

Mailbox. These are for real people and these are the ones you pay for. Each living person in your organization that requires mail, will have a Mailbox. Each person can also have an alias for each domain that you have verified, i.e.,, You decide which of these is the default email address of the user, but mail sent to any of these addresses will all go into Mary’s inbox.

Group. Also known as Distribution Groups are free. These should be for internal use, i.e. When an email is sent to, each person who is a member of this group will receive an email into their own mailbox. If they reply, the reply will come from the user, and the reply will go out to all members of the group also. Examples of typical groups might include, etc. Groups can also have aliases like Mailboxes.

Resource. Also known as Equipment Mailbox or Room Mailbox are free. These are used for reserving and coordinating Rooms and Equipment. For example or By including a Resource in a meeting request or calendar item, you are reserving the Resource for that time period. When you create your calendar event you can look at the Resource to check its availability.

Contacts. Also known as Mail Contacts are free. Mail Contacts typically contain information about people or organizations that exist outside your Exchange organization. Mail contacts can appear in your organization’s shared address book and other address lists, and can be added as members to distribution groups. Each contact has an external email address, and all email messages that are sent to a contact are automatically forwarded to that address. Contacts are ideal for representing people external to your Exchange organization (in the shared address book) who don’t need access to any internal resources.

Shared. Also known as Shared Mailboxes are free. This is the one that is not being utilized properly, if at all, by most organizations. Let’s say you have a generic email address on your website for that you want five people in your organization to receive. Too often we see these being setup initially as Distribution groups. What happens is an email sent to this address goes into the inbox of the 5 recipients, just like an email sent to them directly does. If they reply, it comes from the individual replying. Even if the user creates a rule to automatically move these to a subfolder in their inbox, it does not take long before this proves cumbersome. What I find most Office 365 users doing next is biting the bullet and creating a paid account for sales so it can have a mailbox. Then each of the five people, need to add the account to their Outlook client with the username and the password for the sales account. Don’t even try to tell me that you have not done this. While I am sure Microsoft loves you, this is what Shared Mailboxes are for. Plus they are a snap to administer with no end-user intervention required.