why do only some of my virgin emails come through on my Apple mail box? I know they do not all appear because if I go online and logon Virgin Media, there are always some which have not appeared in my mail box. Why?

Recently I was informed by Virgin Media that my virgin email address is going to be discontinued because I am not a paying member. So I decided to create a new email address using Google's gmail. I use Yosemite 10.10.1 on my Macbook Pro if that's any relevance. I set my Apple mail box up to receive all my email addresses: icloud, gmail and virgin. However, I am not receiving all my virgin emails. I know this because I have had queries as to why I have not responded to a particular email, and if I go on Virgin Media's site and logon on to my account, I find that there are lots of emails which have not appeared in my Apple mailbox. Why is this happening and how do I get all my virgin emails?