If your ISP uses the ORBS open-relay blocking system, then you will not receive e-mail from Empeg. They use PSI.net in the UK which has a bunch of open relays (well, actually, they accept mail from their customers' open relays, but the end result is the same), and so they're on the list.

You may want to ask your ISP to unblock them specifically (the uk.psi.net servers), or use a freemail (such as Yahoo! Mail) for your empeg communications. I had that problem myself just the other day. :)