JohnOrrett
"via Pop3, only new emails come through. "
Yes that's normal, it's the way POP3 is designed to work.
"If I change the settings on the new laptop to IMAP, will all of the existing emails and sub folders then populate?"
Yes, but.....
1) You cannot simply change the incoming server in the existing Outlook settings from pop3.virginmedia.com to smtp.virginmedia.com.
You will need to set up a new email account in Outlook using the IMAP option.
2) The IMAP account will then mirror the structure and content of your friend's VM email account as displayed in their webmail account on the VM website.
So any folders that have been set up in the POP3 Outlook (such as their sent emails) will not appear in their webmail account and so will not be downloaded to the new IMAP account in Outlook,
So if you want to include them then you will need to do something like you are suggesting with PST files.
One big difference they will see is that when they send a VM email using Outlook it will also appear in their VM webmail account. POP3 is strictly a one way process simply downloading new emails to Outlook,
However, IMAP's two way process does also mean that if they delete a VM email in Outlook it will also disappear from their webmail account - and vice versa.
When you set up a new IMAP Outlook, it should auto fill the SMTP and IMAP server details but if you need them:
IMAP settings
Host Name: imap.virginmedia.com
Username: your full Virgin Media email address
Password: your Virgin Media email app password
Advanced settings
SSL Encryption: Enabled
Port: 993 (this may be automatically chosen by selecting SSL encryption)
Note also, that the password in the email Outlook, or any other email client/app, does need to be your friend's VM mail app password. If necessary here's recent post where I set our how to generate a new one Using Thunderbird email client | Virgin Media Community - 5686390
Coenoby