I'm not receiving emails from one particular source. When this happened before, I was able to talk to a technician who fixed the problem. Nowadays, I simply cannot get through to talk to anyone at Virgin.
If it's a personal e-mail address, check the Blacklist in the settings and see if that e-mail has been accidentally blacklisted. Also, check if you have the setting to automatically reject all SPAM messages. Sometimes when I had that level of SPAM filtering it kind of filter out a lot of e-mails.
If you have NTL or Bluyoder, I don't know how those look, but it might be the same as these.