I have setup my SMTP email and when I go to send an email to a member of staff, the email does not deliver to them.
However, when I went on the ‘Free Learning’ and signed this staff up as a mentor, the email was sent to them straightaway so the SMTP settings MUST be correct?
Does anybody know why it is doing this?
This sounds somewhat mysterious. On your server, you will have some mailing logs. These are in different places on different operating systems. For example, in Ubuntu Linux, they are under /var/log/mail.log. If you use shared hosting, you might need to contact your host to get access.
Can you check your logs immediately after sending the email to staff to see if there are any relevant log entries?