The virgin media email does block some domains, I cannot send an email to myself from mail.com, it does not block gmail, I have tested that and many spammers now use gmail as they are not blocked.
I have myself posted on this issue of email blocking, but there were no answers from the community/forum
By doing my own tests, it proved virgin email does block some domains and a message that the email not delivered due to spam listings of the ip address range used by the mail client. (spamhause)
Virgin should not be blocking any personal emails, they should let all emails through that are not blacklisted in settings.
It means that genuine emails may not get through, but spam does get through, the opposite of what should happen.
I suggest you do few tests and would be wise to have alternative emails and switch to them to ensure things like account recovery emails will always work.
I find any of the free emails are good, gmail.com, outlook.com, yahoo.com etc and they are more secure having 2 factor authentication but need to be kept active as some will close if not used for a period usually 12 months but some are 90 days like virgin email.
I no longer use virgin email for my accounts but still use it for junk, just newsletters etc. as a throw-away email.
I was getting 50 spams a month so am now filtering them to discard which works well.
The auto forward on virgin email can also fail on occasion, if it does not like the email for some reason, the auto forward does not work on all emails.
Best to look for alternatives to virgin email is my advice, I have done that 4 years ago, and it means you are not tied to a particular isp provider, and with account recovery use both email and mobile sms text so if one fails the other may work, some accounts allow 2 recovery emails and more that one mobile number.