POP protocol is what your email program uses to receive emails, usually from your ISP. SMTP is a protocol used to send emails out. When we host your website, you will have your own POP and SMTP mail server, meaning you'll be able to both send and receive emails under your own domain name instead using the email address allocated to you by your ISP. However, some ISPs including Telstra and Optus often block your ability to send email via someone else's mail server. In that case you have to ask them to unblock Port 25 for you.