Firstly thank yo for the response, it does make sense what you are outlining; however its slightly different.
The E-mails from this secondary account have been deleted/removed, it does not matter if you access via Virgin Media Email, and/or 3rd party application like iOS E-mail and/or Outlook, the inbox is still empty.
Its strange as all the sent items in the Sent folder are intact.
Nothing is in the trash either, as they have not been deleted in error, they have all just disappeared.
I'm finding that Virgin Media E-mail as a service as a whole, does have general access issues. I have had issues with syncing in the past with my own primary personal account, and when it does sync it seems to miss specific blocks of E-mails, which luckily for me I back-up important ones as and when they come in.
My concern here is where have these E-mails from the secondary account gone? Why would they be removed without a user's authorisation? And who has removed them?
This is the key thing for me to try and understand, if the E-mails have been removed, without any form of recovery, this is something we will have to live with; however how can this be prevented again. Without understanding the Where, Why, and Who, its impossible for this to prevented in the future.
Finally late yesterday evening when we found that this was happening, new E-mails were on occasion being received; however after 10-15minutes they were disappearing from the Inbox, which was not the act of the user, they were just diserpearing.
This has never happened before, it only started from around 20:30 onwards on the 27/09/2020.
As there is no one for you to call to specifically talk about this issue, again there is no way of tracking with Virgin where this problem is occuring.
Sounds like an auto forward has been put in place, can you open up webmail and once theree click on the three lines on the right of the page, select settings, once the settings page is open, on the left click on email and then auto forward, make sure there is no auto forward there, best way is too untick enable.
If there is an auto forward there and you do not reconise the email address then II would recommend changing the email passwoord, as somebody has entered this without your knowledge.