[Jaymoss]

Outlook desktop app to Outlook desktop app and to be honest the OP could just just set it up to pull the VM email into that and it will just sync all folders and then from there you can move everything to your new address. I have 5 email account pulling into my outlook desktop app and one of them is Gmail that in turn pulls multiple legacy email addresses that did used to include ntlworld.com mail . So all my email is synced into Outlook desktop app and then I back up system images so never have to do clean installs so it is all very safe

If they do not want to do it using Outlook app just make sure your VM email has no 2FA and you can just pull it all into gmail. I overcomplicated my answer as it appears plenty of others have too