As a general rule*, you need to use the SMTP (outgoing mail) server of the internet provider you're actually connected to at the time - not the one who provides the mail. They tend to check your IP address, so if you try to send via e.g. O2 UK when you're on Orange in France, it won't work. Try smtp.<provider>.fr e.g. smtp.wanadoo.fr , smtp.orange.fr etc.
* yes, there will be exceptions
Last edited by bnt; 24th Oct 2012 at 18:58.