This week I've had exactly this issue as many others on here have. Yes, Ive read the forum posts and tried everything they recommended including those from Virgin but still the same error.
It has been perfectly fine for year upon year before this week, but now I cant sign into my emails "online" no matter what browser I use.
I've used all those recommended by the posts on here, chrome, Firefox etc etc. I've tried to access the emails on my laptop, iPad and phones via different browsers but get the same "Forbidden" message.
Strange as using outlook on my desktop PC its fine, but a real pain when I'm out and need access online!
please fix asap