@Graham_A
/shrug, mine does (though it's residential, not business).
i guess you mean the business service?
possibly - though it's also possible that OP has assumed he can use it, since it's his ISP's smtp server - (granted, i got it wrong, it should have been .com).
just trying to solicit some more information from OP to understand what they are trying to achieve, and how they have it configured currently.