Exchange Shared Mailbox: Converting a User Mailbox

Converting an Exchange 2007 Mailbox to a Shared Mailbox

When someone leaves the business but their mailbox still needs to be accessible to a team — a departed employee’s inbox, or a generic mailbox that used to belong to a licensed user — converting it to a shared mailbox with the Exchange Management Shell is the cleanest option, since shared mailboxes don’t need their own Exchange CAL in the same way a regular user mailbox does. Run the following from the Exchange Management Shell, replacing the identity with the mailbox in question:

Set-Mailbox -Identity "jsmith" -Type Shared

You can confirm the change afterwards with:

Get-Mailbox -Identity "jsmith" | Select Name, RecipientTypeDetails

which should now report SharedMailbox rather than UserMailbox. Once converted, grant the relevant staff Full Access and/or Send As permissions with Add-MailboxPermission so they can open it from Outlook. If you’re managing this on a modern, supported Exchange environment (on-premises 2016/2019 or Exchange Online), the same cmdlet and syntax still applies — this isn’t something that changed between versions.

Doing This in Exchange Online

The exact same Set-Mailbox -Identity "jsmith" -Type Shared command works unchanged in Exchange Online — connect via the Exchange Online PowerShell module first (Connect-ExchangeOnline), then run it against the cloud mailbox identity. A couple of things worth doing at the same time in a cloud environment specifically:

• Once converted, the mailbox no longer needs an Exchange Online licence for the first 50GB of storage — if the departing user’s licence was dedicated to this mailbox, this is the point to remove or reassign it. Exceeding 50GB requires stepping up to Exchange Online Plan 2 (or Plan 1 with the Exchange Online Archiving add-on).
• Access is auto-mapped into the delegate’s Outlook by default the moment you run Add-MailboxPermission -AccessRights FullAccess — add -AutoMapping $false if you’d rather the mailbox not appear automatically for everyone you grant access to.
• If staff need to reply “as” the shared mailbox without full access, Set-Mailbox -GrantSendOnBehalfTo is usually a better fit than Send As permissions.

Resources

• Exchange
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