Outgoing mail problem with two isp's

I live in the Netherlands. I use my iPhone on wifi in my second home in Belgium. Obviously I turn dataroaming off, since this would cost me a fortune. The mail server I use in my first home rejects outgoing mail when I am not connecting through this isp. In my second home I have an adsl connection with a wireless router. Sending mail from the macbook is no problem, after trying the first smtp server it comes up with the question if I want to use another smtp server.
In the iPhone however, I can set alternative smtp servers but when I try to send mail I get the message 'Cannot send Mail. The server rejected one of the recipients addresses'. Of course the address is correct. I created a new account with the Belgium smtp server as the first one and this works OK. But I want to be able to reply to a message in my normal account. How do I solve this?

Arjen

 

Setting the outgoing mail server to gMail is an idea worth trying.

Thanks,

A