Exchange as 3rd prty email get around

I recently switched my DSL provider to earthlink. I explained to them what i had including and exchange server. After I was setup I noticed I could recieve email to my domain but not send out. After much testing and reconfiguring and failing I called them to find out they don’t allow 3rd party email. I understand there may be a way around this with out directing my outgoing to earthlinks smtp which shows my emailing coming from earthlink and not the domain.

Any help would be greatly appreciated.
Thanks