Not receiving all emails (virgin.net)
I signed-up to an online course today and found that I didn't receive a confirmation email, or any of the OTP emails that they send for logging in. I obviously checked they weren't going into my Spam folder, which they weren't.
I contacted the course provider and they could see the messages failing to be delivered to my virgin.net address (Error: "retry time not reached for any host for virgin.net"). I gave them an alternate, non-Virgin email address to try instead, and their emails came straight through to that, which leads me to believe Virgin are dropping messages (perhaps due to over-aggressive spam filtering) without even flagging them as possible spam, or sending a notification to the user to let them know an email sent to them has been dropped at the server end.
I've also had the exact same problem with an online shop I've used quite a few times, and I never receive any of their emails if I use my normal virgin.net email address. This is a major problem, as it means I have no idea what other emails you might also be failing to deliver to my Inbox.