If there was a general problem with traffic between Sky.com and VM addresses, I would expect to see dozens of posts on the subject, not just the odd one or two.
Whilst waiting here for a further response from VM I suggest you send a test email to the Sky address relative – allow a few hours for delivery - and then telephone him to check points (a) to (d) below –
(a) that he only uses one address and that is the one you sent it to
(b) whether it arrived in his Inbox or not
(c) whether he uses any email filters, say, to delete incoming spam
(d) is it in his spam folder?
and finally
(e) ask him to send an email to you.
PS
I have no problem logging-in to The National Lottery site and buying tickets using a credit card.