As mentioned above you will need to go through the process of generating an app password to use with the mail app on your phone.
https://www.virginmedia.com/help/broadband/manage-email-account. See the FAQs on this help page.
The steps you need to follow are:
• Sign in to My Virgin Media
• Go to Account settings, then Account details
• Tap Manage next to Manage your Virgin Media Mail app password under Virgin Media Mail
• Then, under Virgin Media Mail app password tap Get password
• Continue the flow and a new secure password will be generated, and the mailbox unlocked
• Update any third-party apps that may be use to access your Virgin Media Mail emails with this new app password.