Thousands of Virgin Media National broadband customers will lose their email address, as they transfer over to TalkTalk's network.
Virgin Media is in the process of migrating its remaining 100,000 non-cable customers to the broadband provider, having taken the decision to cease ADSL operations.
The cable giant says the transfer to TalkTalk will be "seamless", with no broadband downtime for any of its remaining non-cable customers.
However, Virgin Media is shutting down its virgin.net domain, and as such, National subscribers will have to adopt new email addresses, reports the Telegraph.
Those who are moving to TalkTalk will have 12 months to set up a new email account, but consumers switching to another provider will only have 90 days.
A spokesperson for Virgin Media said the company had explored "all avenues" in a bid to maintain the virgin.net domain, and allow customers to keep their email addresses.
However, he admitted that none were financially viable for the service provider.
In a bid to make the switchover as simple as possible, the firm is creating help guides and videos.