With LGfL, they are quite strict on what devices on their networks send email. However, they are happy for you to make use of Google’s SMTP server.
Things like Profile Manager make use of email for inviting users onto the Managed Distribution programme, so I wanted to setup our Mac server to be able to send emails like that. After a bit of searching, I came across this brilliant explanation of how to send mails from localhost. And it seems to have done the trick!