That question re emails from email@e.virginmedia.com was asked earlier this year on this thread https://community.virginmedia.com/t5/Email/Is-this-email-from-Virgin-real-or-is-this-spam
Scroll through to post /message 6 for an official answer from Virgin Media.
Basically, the answer is that provided you have previously registered your interest with VM then the email is real.
However, read all the way through the thread I have linked to and check that your email is the same as they were discussing there . 😉
Coenoby
I'm a Very Insightful Person, I'm here to share knowledge, I don't work for Virgin Media.
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