These will work for both Exchange 2010, Exchange 2013, 2016 and Office 365.
Make a new shared mailbox:
New-mailbox "Mailbox Name" -shared –userprincipalname [email protected] -OrganizationalUnit "domain.com/OU1/OU2/OU3" -Database MBX-DB-1
If you already have the mailbox and want to set it to a shared mailbox use this:
Get-Mailbox -Identity alias@ccompany.com | Set-Mailbox -Type Shared
Grant Full Access Permissions to your new shared mailbox:
Add-MailboxPermission -Identity Mailbox Alias -User User Alias -AccessRights FullAccess
Grant Send As permissions to your new shared mailbox:
Get-user -identity mbx-alias| Add-ADPermission -User username -ExtendedRights "Send As"
List Users with Full Access to a Mailbox
Get-Mailbox -identity "alias" | Get-MailboxPermission | where { ($_.AccessRights -eq "FullAccess") -and ($_.IsInherited -eq $false) -and -not ($_.User -like "NT AUTHORITY\SELF") | List User, DisplayName, PrimarySmtpAddress }
List Mailboxes a user has full access to:
List all mailboxes to which a particular user has Full Access permissions:
Get-Mailbox | Get-MailboxPermission -User alias