Understand my email sending limits
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.
Check Bulk Senders Guidelines for Virgin Media Mail about best practices for sending a large amount of mail through Virgin Media Mail.