How many times do we have to say that this is a public forum and like all such forum is regularly scanned by web bots and humans for viable e-mail addresses to use for spam? . The Forum rules are clear on this point. - do not post private information. I have rejected your image to protect your privacy. Edit it and repost if you want to, but I see apcyberax has answered your question now. .
As a Very Insightful Person, I'm here to share my knowledge. I don't work for Virgin Media.
Thanks for your help but, unfortunately, I've still got the same problem and I think it's down to my User Account having a fault in itself. I set up another user account and, in there, the Mail works perfectly normally. I'm still able to look at emails in my Virgin Media Mail account so, at least, I've still got that.
I really wonder if it's worth bothering with Apple's Mail.