Today's tip is a quick one: If you have licensed mailboxes you only need as additional E-Mail addresses with a separate E-Mail address you can think about converting them to shared mailboxes. Shared Mailboxes have 10GB free storage and there are no additional license costs. Setting the appropriate rights to the shared mailbox they will also automatically show up in Outlook.
If you want to convert one of your licensed mailboxes to a shared mailbox you can do that with PowerShell.
First, connect to Exchange Online:
$UserCredential = Get-Credential
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection
Now, check, if the Mailbox is not too large for being converted (more than 10 GB).
Get-MailboxStatistics <Alias> | FL Total*
Now, convert the Mailbox:
Set-Mailbox -Identity [alias] -Type "Shared" -ProhibitSendReceiveQuota 10GB -ProhibitSendQuota 9.75GB -IssueWarningQuota 9.5GB
Shortly after you've set that the mailbox shows up under the sahred Mailboxes. You are now save to remove the license from it and use it for a real User account.