There is some useful information here:
That helped me get the outgoing mail going through gmail, but I was trying to do it through my ISP, but couldn't get it to work.
I might just have to stick to gmail, the only problem is that the recipient receives an email from my gmail account, where as I would have preferred it to come through as the account I am sending from, i.e. my domain.
I wonder if this is a setting in gmail, anyone know?