My elderly mum was on Virgin (via ntlworld) for many many years, and only left when she moved house and was obliged to take-up another ISP (for the record, TalkTalk, and that is another very sorry tale) ..
Unfortunately no-one from either Virgin (or TalkTalk) informed mum that she needed to configure "Email forwarding" when she left Virgin and now more than 90 days have passed so we can no longer access the Virgin media portal to do this ourselves.
Surprisingly, I can still access her ntlworld [Virgin] Email account via an imap client (Outlook, Em etc) and read/send emails from there; but what I want to do is set up email forwarding (e.g. .forward address) so that incoming emails will be automatically forwarded to her new email address. Virgin front line support tells me this is not technically possible however, given that her account is clearly still live to some degree (as I can still read her emails and send from there) this must be possible for a superuser [su] (or equiv) to do.
For forwarding to work, you have to have an active Virgin Media email address to send the mail to in the first place. Once the mail closure is complete, this is no longer the case, so for once 1st line support were actually correct in what they were saying (a rarity :)).
If you still have POP3/IMAP access then you can configure the mail program to forward arriving mail to her new email address when it picks up new mail from the server, but once the account is closed completely the mailbox is deleted from their system. The email team are unlikely to set up automatic forwarding for an account that's in the process of deletion.
Once webmail access has gone, you need to think about backing up mail from the server before POP3/IMAP access is removed completely anyway.
As a Very Insightful Person, I'm here to share my knowledge. I don't work for Virgin Media.
Now that 90 days have passed, “drop the hammer”, and make sure Virgin Media delete the unsupported email account(s) because the risks from continued use far outweigh any perceived benefits (IMHO). If knowing this you still wish to continue using the unsupported email account(s) then consider:
accessing it from your new email service if it supports third party email account via POP3
create a new temporary email address with a service that supports third party email account via POP3 and forwarding to send message on to the new email address