I think you've hit the nail on the head Chris. My Freeserve account isn't one of the freebie jobs (though I do have a freebie fsnet.co.uk account as well which I access via Orange webmail).
Today, I have been having an identical problem with a friend who has broadband with Orange. Email messages sent to me WITHOUT attachments all 'get through' the Orange server BUT any sent WITH an attac ...
Most if not all outgoing mail problems from Orange/Wanadoo/freeserve accounts could be put down to the fact that a number of their mail server IP addresses are in the Spamhaus Block List (SBL).
