As @用心棒 has said if those emails are being "spoofed" it means that they are not actually coming from your Virgin Media email account.
There has always been a basic weakness with all email in general in that the email address in the From: and Sender: fields in an email header does not have to be the email address that the email actually comes from.
A spammer can send simply forge the From: and Sender: details in an email to make it appear that it is coming from your VM email account, (or anyone-else's account come to that) and they do not need access to your VM email account or the VM email servers to do that.
Therefore, once a spammer knows your email address they can continue to spoof emails so they appear to come from your address even though the email account itself no longer exists.
Scammers spoof email addresses to make the recipient think the email is coming from a trusted source, (your bank for example).
Spammers do it to simply hide their own email address and ensure that any rejection or non delivery messages that get generated by their spoofed emails are sent to your email address not theirs!
Here's a good overview of what spoofing is and how it's done https://www.proofpoint.com/uk/threat-reference/email-spoofing
Sadly, there is nothing that can be done by VM to stop them continuing to send these spoofed emails.
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