Office 365 SMTP Relay Using Windows PowerShell

We are looking to the future, and getting ready to remove OnPrem Exchange.  To do this we need to deal with SMTP Relay.

Microsoft have this doc to help: https://support.office.com/en-gb/article/How-to-set-up-a-multifunction-device-or-application-to-send-email-using-Office-365-69f58e99-c550-4274-ad18-c805d654b4c4

But I wanted to code it ;-)

Quite simple, you need to use an Exchange Online Account:
$Password = "#mailbox password"
$emailFrom = "#mailbox"
$SMTPServer = "smtp.office365.com"
$SMTPPort = 587
$emailTo = "#recipient"
$msgsubject = "testing testing 1-2-3"
$msgBody = "hello world"
$message = New-Object Net.Mail.MailMessage($emailFrom, $emailTo, $msgsubject, $msgBody)
$message.IsBodyHTML = $True

$smtp = New-Object Net.Mail.SmtpClient($SMTPServer,$SMTPPort)
$smtp.EnableSSL = $true
$smtp.Credentials = New-Object System.Net.NetworkCredential($emailFrom, $Password);
$smtp.Send($message)

enjoy