what's stopping the OP's show.
Basically, he is a customer of a company called Virgin. Virgin acquired a company called NTL:Telewest. NTL:Telewest is the byproduct of the merger of, yes, you guessed it ... NTL and Telewest. These companies in turn are the amalgamation of a number of smaller local cable companies that sprung up during boom times.
So in essence, "old habits die hard" as they say. And what you get as a Virgin customer is dependent on which "region" you are in. The legacy companies had two different email systems ...... you get the drift.
There is no technical reason why he should not be able to get his email transferred, merely a business one to do with what policies and infrastructure were transferred during all that M&A activity over the years.
I know some providers try to block TCP port 25 (and 465?) to try and force you to use their own SMTP servers but that can't be
And this is a very, very good thing. I think all residential internet connections should have port 25/465 blocked by default. Users should be forced to demonstrate technical competence and consent to automated security scanning before the ISP even considers unblocking.
The amount of spam that originates from virus infested home-computer zombie-nets is simply staggering (generally said to be around 80%-90% of the worldwide spam volume).
You should also bear in mind that there are special lists available to ISPs and other relevant parties (e.g. vetted businesses) that contain the IP ranges of other ISPs home customers. Therefore even if your port 25 is open, you may find your messages never get through because the receiving ISP quite rightly blocks the spam sources.