I'm having difficulty sending e-mails from my Demon account on my iPhone 3G. I've set it up to use post.demon.co.uk as the primary outgoing mail server and I've added smtp.o2.co.uk as an alternative. I'm in the UK. When I'm out and about it comes up with the error - Cannot Send Mail "One of the recipient addresses was invalid". This is the case on 3G and any other connection. When I'm at home and on wi-fi it works fine! The addresses I'm using are correct as they work from home and on my other account! My .mac/MobileMe account works perfectly. I use Demon for my business and .mac for the family. Any ideas?