it could be the e-mail settings perhaps - some ISP mail servers have the same for incoming and outgoing, for example (using bt as this example) mail,bt.com or pop3.bt.com ,. some however have different for outgoing such as smtp.bt.com , if you go into outlook express, tools , accounts, click on the e-mail account and then properties - then servers, this shows what has been set up - you could then look on google for your ISP mail settings to double check - is this a recent problem or has it always been like this?