Same issue for me, I have sent and recieved at least 25 emails today, and this issue has just come on.
I have tried logging directly onto web email, as I managed to do earlier today, but now I get the follwoing message, so I guess there is an issue
Your mailbox is not available at the moment.
Please retry again in one hour and make sure you are using the correct password to access your email from all of your devices.
If the problem continues, please call our team for help on 150 from a Virgin Media phone or mobile, or 0345 454 1111 from any other phone and select option 2. For details about how much it costs to call our team from a Virgin Media home phone, visit virginmedia.com/callcosts. Call costs from other networks and mobiles vary.