They may not be disapearing, there are many things that could be happening, do you get an error message at all? What ISP are you sending through(NTL, Wanadoo etc), what is the recipient ISP (Wanadoo, NTL etc), what are you sending through (Outlook, Outlook Express etc) and do you run any firewalls or Anti-virus? It also could be getting picked up as possible Spam by the new strict filters put in place by NTL.
http://www.cableforum.co.uk/board/sh...9&page=1&pp=15