Create a New Shared Mailbox

1. Connect to Exchange Online via PowerShell

   Connect-ExchangeOnline
   

2. Create the shared mailbox

   New-Mailbox -Name "Shared Mailbox Name" -DisplayName "Shared Mailbox Name" -Alias "SharedMBName" -Shared -PrimarySmtpAddress "SharedMBName@contoso.com"
   

3. Either add users who need access to the mailbox via the Exchange admin center OR via the following commands

   # Create a variable and add individuals to it as an array
   $Users = @("FirstName1.LastName1@contoso.com", "FirstName2.LastName2@contoso.com", "FirstName3.LastName3@contoso.com")
   
   # Using a foreach loop, add "Full Access" and "Send As" permissions
   foreach ($User in $Users) {
   
   #Full Access
   Add-MailboxPermission -Identity "SharedMBName@contoso.com" -User $User -AccessRights FullAccess -InheritanceType All
   
   #Send As
   Add-RecipientPermission -Identity "SharedMBName@contoso.com" -Trustee $User -AccessRights SendAs -Confirm:$false
   }
   

4. Verify access rights via the Exchange admin center or via the following command(s)

   # Basic view
   Get-MailboxPermission -Identity "SharedMBName@contoso.com"
   
   # Detailed view
   Get-MailboxPermission -Identity "SharedMBName@contoso.com" | fl