In an effort to fight spam and prevent abuse, Virgin Media will temporarily disable your account if you send a message to more than 500 recipients or if you send a large number of undeliverable messages. If you use a POP or IMAP client (Microsoft Outlook or Apple Mail, e.g.), you may only send a message to 100 people at a time. Your account should be re-enabled within 24 hours.
If you send a large number of undeliverable messages, we suggest verifying your contacts' email addresses. It's also important that everyone you are sending mail to is willing to receive it.