The obvious conclusion to draw from what you have said is that the addresses which do not appear in your current VM account in My Virginmedia were created on a different account. You probably moved home and didn't have the addresses transferred across when you moved or similar. You can get the addresses transferred across now but it is not a reliable process and also any or all of the addresses on your current VM account will be wiped out and all the mail content lost. The process is called move and transfer. You can never re-create the addresses on your current account, for security reasons.
If you want the VM staff here to investigate then wait here for them to respond. Wait time about a week.
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